ACUS01 KWNS 081236
SWODY1
SPC AC 081234

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0634 AM CST Mon Dec 08 2025

Valid 081300Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected through tonight.

...Synopsis and Discussion...
Within broad upper troughing over the eastern CONUS, an embedded
shortwave trough will move across the southern Appalachians to
coastal VA/NC by this evening. A surface cold front will sag south
across the remainder of the FL Peninsula. In the wake of earlier
convection, daytime heating will be needed for the redevelopment of thunderstorms along the front. Besides modest low-level convergence
with the front, large-scale ascent will remain weak across this
region. This, combined with persistently poor mid-level lapse rates,
should limit convective intensity. Still, a locally strong gust or
two may occur until the front moves into the FL Straits.

..Gleason/Jewell.. 12/08/2025

$$

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ACUS01 KWNS 081604
SWODY1
SPC AC 081603

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1003 AM CST Mon Dec 08 2025

Valid 081630Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected through tonight.

...Synopsis and Discussion...
A progressive upper pattern will persist today with a pair of
shortwave troughs, one currently moving towards the central
Appalachians and the other moving towards the Four Corners and
central Rockies, continuing eastward/southeastward as another pair
of shortwave troughs drop into the northern Plains and Upper
Midwest. At the surface, high pressure will continue to shift eastward/southeastward over more of the eastern CONUS while a low,
currently in the western Atlantic off the SC coast, progresses
northeastward.

A cold front extends southwestward from the western Atlantic surface
low through central FL, which is the only area across the entire
CONUS with any notable low-level moisture. Dewpoints over south FL
preceding this front are currently in the low 70s, and mesoanalysis
indicates modest buoyancy over the region. Convergence along the
front will be modest and much of the large-scale ascent will be
displaced north and east of this region, but isolated showers and
thunderstorms are still expected this afternoon and evening.
Moderate deep-layer vertical shear is in place, and there is a very-low-probability risk for a damaging gust or two. However,
limited updraft depth and/or persistence should mitigate the overall
severe potential.

..Mosier/Leitman.. 12/08/2025

$$

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ACUS01 KWNS 081940
SWODY1
SPC AC 081938

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0138 PM CST Mon Dec 08 2025

Valid 082000Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected through tonight.

...20z Update...
The previous forecast remains on track with no changes required.
Recent updrafts developing across far south FL have been slow to
intensify within the modestly buoyant but weakly forced environment.
This trend is expected to continue through this evening as the front
continues to push offshore.

..Moore.. 12/08/2025

.PREV DISCUSSION... /ISSUED 1003 AM CST Mon Dec 08 2025/

...Synopsis and Discussion...
A progressive upper pattern will persist today with a pair of
shortwave troughs, one currently moving towards the central
Appalachians and the other moving towards the Four Corners and
central Rockies, continuing eastward/southeastward as another pair
of shortwave troughs drop into the northern Plains and Upper
Midwest. At the surface, high pressure will continue to shift eastward/southeastward over more of the eastern CONUS while a low,
currently in the western Atlantic off the SC coast, progresses
northeastward.

A cold front extends southwestward from the western Atlantic surface
low through central FL, which is the only area across the entire
CONUS with any notable low-level moisture. Dewpoints over south FL
preceding this front are currently in the low 70s, and mesoanalysis
indicates modest buoyancy over the region. Convergence along the
front will be modest and much of the large-scale ascent will be
displaced north and east of this region, but isolated showers and
thunderstorms are still expected this afternoon and evening.
Moderate deep-layer vertical shear is in place, and there is a very-low-probability risk for a damaging gust or two. However,
limited updraft depth and/or persistence should mitigate the overall
severe potential.

$$

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ACUS01 KWNS 090049
SWODY1
SPC AC 090047

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0647 PM CST Mon Dec 08 2025

Valid 090100Z - 091200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorm potential appears negligible tonight.

...Discussion...
With the surface cold front having recently pushed off the FL
Peninsula/Keys, dry/stable conditions will mitigate
lightning-producing convection across the CONUS tonight. Isolated
thunderstorms are possible offshore across the FL Straits as the
boundary slows/stalls.

..Grams.. 12/09/2025

$$

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ACUS01 KWNS 090503
SWODY1
SPC AC 090502

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1102 PM CST Mon Dec 08 2025

Valid 091200Z - 101200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorm potential appears negligible today through tonight.

...Discussion...
Conditions will be too dry/stable for lightning-producing convection
across the CONUS through the period. Isolated thunderstorms are
possible today across the FL Straits near a quasi-stationary front
that progressed offshore of the FL Peninsula/Keys on Monday.

..Grams/Jirak.. 12/09/2025

$$

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ACUS01 KWNS 091238
SWODY1
SPC AC 091236

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0636 AM CST Tue Dec 09 2025

Valid 091300Z - 101200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...Synopsis and Discussion...
A cold front has settled southward while decelerating over the FL
Straits this morning. Appreciable low-level moisture to support
thunderstorms is expected to remain along/south of this boundary,
with little potential for convection over land through tonight.

..Gleason/Lyons.. 12/09/2025

$$

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ACUS01 KWNS 091616
SWODY1
SPC AC 091614

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1014 AM CST Tue Dec 09 2025

Valid 091630Z - 101200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...Synopsis and Discussion...
Upper pattern will remain active today/tonight as a low-amplitude
shortwave trough progresses quickly eastward through the OH Valley
ahead of a more substantial shortwave trough moving southeastward
out of the Canadian Prairies and through the northern Plains and
Upper Midwest. By 12Z Wednesday, this second shortwave will likely
extend from the Lake Michigan vicinity southwestward into northeast KS/northwest MO.

Progression of this second shortwave will reinforce the already dry
and stable airmass in place across much of CONUS, precluding
thunderstorms. Some modest moisture return is anticipated late
tonight/early tomorrow across the western Gulf, but much of this
moisture will remain offshore. Some low-level moisture also remains
in place across south FL, even in the wake of the cold front now
settled across the Florida Straits. Even with this low-level
moisture still in place, modest and shallow buoyancy, and limited
forcing for ascent should preclude thunderstorms across south FL
today.

..Mosier/Moore.. 12/09/2025

$$

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ACUS01 KWNS 092036
SWODY1
SPC AC 092034

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0234 PM CST Tue Dec 09 2025

Valid 092000Z - 101200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

No changes.

..Hart.. 12/09/2025

.PREV DISCUSSION... /ISSUED 1014 AM CST Tue Dec 09 2025/

...Synopsis and Discussion...
Upper pattern will remain active today/tonight as a low-amplitude
shortwave trough progresses quickly eastward through the OH Valley
ahead of a more substantial shortwave trough moving southeastward
out of the Canadian Prairies and through the northern Plains and
Upper Midwest. By 12Z Wednesday, this second shortwave will likely
extend from the Lake Michigan vicinity southwestward into northeast KS/northwest MO.

Progression of this second shortwave will reinforce the already dry
and stable airmass in place across much of CONUS, precluding
thunderstorms. Some modest moisture return is anticipated late
tonight/early tomorrow across the western Gulf, but much of this
moisture will remain offshore. Some low-level moisture also remains
in place across south FL, even in the wake of the cold front now
settled across the Florida Straits. Even with this low-level
moisture still in place, modest and shallow buoyancy, and limited
forcing for ascent should preclude thunderstorms across south FL
today.

$$

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ACUS01 KWNS 100051
SWODY1
SPC AC 100049

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0649 PM CST Tue Dec 09 2025

Valid 100100Z - 101200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...Discussion...
A fast moving surface low, associated with a strong mid-level jet
streak, will continue to move east-southeastward toward the western
Great Lakes this evening. Forecast soundings show some very weak
elevated instability within the warm sector, but it does not appear
instability will be deep enough for sufficient charge separation for
any thunderstorm activity. Elsewhere in the CONUS, thunderstorm
activity will be minimal without significant instability in place.
Some lightning has occurred south of the Florida Keys, in the
vicinity of the stalled surface front. However, the lightning
activity has remained well offshore and is expected to remain so.

..Bentley.. 12/10/2025

$$

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ACUS01 KWNS 100556
SWODY1
SPC AC 100554

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1154 PM CST Tue Dec 09 2025

Valid 101200Z - 111200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for thunderstorms appears low today.

...Synopsis...
The large-scale pattern will feature a ridge across the western
CONUS with a trough across the east. A surface low will deepen below
990mb as it moves from the southern Great Lakes to the Northeast
during the period. A cold front will extend southwest from this
surface low and bring a reinforcing cold/dry airmass to much of the
central and eastern CONUS.

Significant moisture (60F dewpoints) will be relegated to far south
Florida. However, even here, northerly flow should persist within
the post frontal airmass. This should keep any thunderstorm
potential well offshore. A brief period of southerly return flow
across the western Gulf may bring some near 60F dewpoints to the
Texas coast, but this should be short-lived as a reinforcing cold
front moves offshore this evening.

Thunderstorms are not expected across the CONUS today.

..Bentley/Thornton.. 12/10/2025

$$

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ACUS01 KWNS 101242
SWODY1
SPC AC 101240

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0640 AM CST Wed Dec 10 2025

Valid 101300Z - 111200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...Synopsis and Discussion...
Rich low-level moisture will remain confined to parts of south FL,
the Keys, and offshore waters today. With a reinforcing cold front
expected to clear the Atlantic and Gulf Coasts through tonight,
thunderstorm potential across the CONUS appears minimal.

..Gleason/Lyons.. 12/10/2025

$$

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ACUS01 KWNS 101623
SWODY1
SPC AC 101621

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1021 AM CST Wed Dec 10 2025

Valid 101630Z - 111200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...Synopsis and Discussion...
A shortwave trough, and accompanying intense jet streak with 500 mb
winds over 100 kt, will continue eastward through the OH Valley
today and off the Northeast coast by early tomorrow. Surface low
associated with this wave will progress northeastward from its
current position over southeastern Lower MI/southwestern Ontario
along the St. Lawrence Valley today, continuing through ME and into
the Canadian Maritimes by early tomorrow. An extensive cold front
extending southeastward from this low will push quickly
eastward/southeastward through the southern Plains and much of the
eastern CONUS, ending the period well off the East Coast.

Passage of this cold front will reinforce the dry and stable
conditions across the majority of the CONUS, precluding
thunderstorms. Modest low-level moisture will remain over
central/southern FL throughout the day, but warm low to mid-level
temperatures will prohibit deep convection, limiting the
thunderstorm potential.

..Mosier/Moore.. 12/10/2025

$$

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ACUS01 KWNS 101911
SWODY1
SPC AC 101910

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0110 PM CST Wed Dec 10 2025

Valid 102000Z - 111200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

No changes.

..Hart.. 12/10/2025

.PREV DISCUSSION... /ISSUED 1021 AM CST Wed Dec 10 2025/

...Synopsis and Discussion...
A shortwave trough, and accompanying intense jet streak with 500 mb
winds over 100 kt, will continue eastward through the OH Valley
today and off the Northeast coast by early tomorrow. Surface low
associated with this wave will progress northeastward from its
current position over southeastern Lower MI/southwestern Ontario
along the St. Lawrence Valley today, continuing through ME and into
the Canadian Maritimes by early tomorrow. An extensive cold front
extending southeastward from this low will push quickly
eastward/southeastward through the southern Plains and much of the
eastern CONUS, ending the period well off the East Coast.

Passage of this cold front will reinforce the dry and stable
conditions across the majority of the CONUS, precluding
thunderstorms. Modest low-level moisture will remain over
central/southern FL throughout the day, but warm low to mid-level
temperatures will prohibit deep convection, limiting the
thunderstorm potential.

$$

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ACUS01 KWNS 110056
SWODY1
SPC AC 110054

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0654 PM CST Wed Dec 10 2025

Valid 110100Z - 111200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast across the U.S. through tonight.

...DISCUSSION...
A mid-level trough, and an associated cold front will move eastward
across the eastern U.S. tonight as northwest flow remains over much
of the western and central U.S. Surface high pressure will remain
over the central U.S. The airmass across the continental U.S. will
remain relatively cool and dry, making conditions unfavorable for
thunderstorms through daybreak on Thursday.

..Broyles.. 12/11/2025

$$

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ACUS01 KWNS 110555
SWODY1
SPC AC 110553

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1153 PM CST Wed Dec 10 2025

Valid 111200Z - 121200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast across the U.S. on Thursday.

...DISCUSSION...
A mid-level trough will move eastward from the eastern U.S. into the
western Atlantic today, as northwest flow remains over most of the
nation. At the surface, a large area of high pressure will be
located from parts of the Great Plains to the southern and central Appalachians. The relatively cool and dry airmass will be
unfavorable for thunderstorm development across the U.S. through
tonight.

..Broyles/Thornton.. 12/11/2025

$$

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ACUS01 KWNS 111249
SWODY1
SPC AC 111248

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0648 AM CST Thu Dec 11 2025

Valid 111300Z - 121200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...Synopsis and Discussion...
Surface high pressure and offshore flow will be maintained today
across much of TX and the Southeast as an upper trough/low advances east-northeastward across New England into Canada. With cool and/or
stable conditions expected across a large majority of the CONUS,
thunderstorms are not expected through tonight.

..Gleason/Lyons.. 12/11/2025

$$

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ACUS01 KWNS 111614
SWODY1
SPC AC 111612

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1012 AM CST Thu Dec 11 2025

Valid 111630Z - 121200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...Discussion...
A broad midlevel trough will move off the Eastern Seaboard today,
while surface high pressure shifts eastward across the Southeast.
Farther west, a weak surface low and accompanying cold front will
advance eastward from the central Plains to the Mid MS Valley.
Dry/stable conditions ahead of/behind the front will limit
thunderstorm potential across the CONUS.

..Weinman.. 12/11/2025

$$

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ACUS01 KWNS 111936
SWODY1
SPC AC 111934

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0134 PM CST Thu Dec 11 2025

Valid 112000Z - 121200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...20Z Update...
No changes needed.

..Mosier.. 12/11/2025

.PREV DISCUSSION... /ISSUED 1012 AM CST Thu Dec 11 2025/

...Discussion...
A broad midlevel trough will move off the Eastern Seaboard today,
while surface high pressure shifts eastward across the Southeast.
Farther west, a weak surface low and accompanying cold front will
advance eastward from the central Plains to the Mid MS Valley.
Dry/stable conditions ahead of/behind the front will limit
thunderstorm potential across the CONUS.

$$

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ACUS01 KWNS 120041
SWODY1
SPC AC 120039

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0639 PM CST Thu Dec 11 2025

Valid 120100Z - 121200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast in the U.S. through tonight.

...DISCUSSION...
At mid-levels, a low will move across far northern New England this
evening, as northwest flow remains in place from the Appalachians
northwestward into the northern Rockies. At the surface, a cold
front will move southward across the central and southern Plains
into the mid Mississippi Valley. Over almost the entire nation, a
relatively dry airmass will be in place, making conditions
unfavorable for thunderstorm development through daybreak on Friday.

..Broyles.. 12/12/2025

$$

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ACUS01 KWNS 120554
SWODY1
SPC AC 120552

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1152 PM CST Thu Dec 11 2025

Valid 121200Z - 131200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast across the U.S. today or tonight.

...DISCUSSION...
Mid-level northwesterly flow will remain in place across most of the
U.S. today and tonight, as a trough moves southeastward into the
Great Lakes region. At the surface, a cold front will move southward
into the south-central U.S., as a cold airmass moves into the
northern states. Overall, conditions will remain dry over most of
the nation today and tonight, eliminating any chance for
thunderstorms.

..Broyles.. 12/12/2025

$$

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ACUS01 KWNS 121255
SWODY1
SPC AC 121254

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0654 AM CST Fri Dec 12 2025

Valid 121300Z - 131200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast across the U.S. today or tonight.

...Discussion...
Cold/continental trajectories especially east of the Rockies will
generally preclude thunderstorm development. Regarding a potential
exception, gradual low-level moisture return will continue to occur
over the western Gulf toward coastal Texas ahead of a low-latitude
trough over northern Mexico. Convection will probably develop and
increase late tonight over the western Gulf, but modest forcing for
ascent and marginal thermodynamic profiles aloft should limit
thunderstorm potential over inland areas of Texas.

..Guyer/Lyons.. 12/12/2025

$$

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ACUS01 KWNS 121622
SWODY1
SPC AC 121620

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1020 AM CST Fri Dec 12 2025

Valid 121630Z - 131200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible in the vicinity of the Lower
Texas Coast early Saturday morning.

...Discussion...
Morning water-vapor imagery indicates an upper-level jet streak
moving eastward across northern MX. The core of this feature will
advance into the western Gulf tonight -- remaining south of TX. In
response, a modest increase in southerly low-level flow will deepen boundary-layer moisture/erode inhibition and yield weak
surface-based buoyancy over the western Gulf and Lower TX Coast
overnight. While most deep convection should be confined to the
higher low-level theta-e plume offshore, strengthening coastal
convergence amid the deepening low-level moisture may support a
couple storms over the immediate coastal areas in the 08-12Z time
frame. A remnant warm layer aloft and weak low/mid-level flow should
limit updraft intensity over land areas.

..Weinman.. 12/12/2025

$$

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ACUS01 KWNS 121946
SWODY1
SPC AC 121945

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0145 PM CST Fri Dec 12 2025

Valid 122000Z - 131200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible in the vicinity of the Lower
Texas Coast early Saturday morning.

...20Z Update...
No changes needed to ongoing forecast.

..Grams.. 12/12/2025

.PREV DISCUSSION... /ISSUED 1020 AM CST Fri Dec 12 2025/

...Discussion...
Morning water-vapor imagery indicates an upper-level jet streak
moving eastward across northern MX. The core of this feature will
advance into the western Gulf tonight -- remaining south of TX. In
response, a modest increase in southerly low-level flow will deepen boundary-layer moisture/erode inhibition and yield weak
surface-based buoyancy over the western Gulf and Lower TX Coast
overnight. While most deep convection should be confined to the
higher low-level theta-e plume offshore, strengthening coastal
convergence amid the deepening low-level moisture may support a
couple storms over the immediate coastal areas in the 08-12Z time
frame. A remnant warm layer aloft and weak low/mid-level flow should
limit updraft intensity over land areas.

$$

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ACUS01 KWNS 130026
SWODY1
SPC AC 130025

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0625 PM CST Fri Dec 12 2025

Valid 130100Z - 131200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible in the vicinity of the Lower
Texas Coast later tonight.

...01z Update...

Low-amplitude short-wave trough is embedded within the southern
stream over deep South TX. This feature is shearing east toward the northwestern Gulf basin where it is expected to encourage isolated
thunderstorm development, primarily off the south TX Coast later
tonight. 00z sounding from BRO was notably capped with strong
inhibition around 2km. Latest model guidance suggests inhibition
will gradually weaken which may allow isolated offshore convection
to gradually approach the coast later tonight. Even so, this
activity should remain weak with the greater concentration holding
offshore.

..Darrow.. 12/13/2025

$$

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ACUS01 KWNS 130539
SWODY1
SPC AC 130537

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1137 PM CST Fri Dec 12 2025

Valid 131200Z - 141200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated weak thunderstorm activity is possible across portions of
the Texas and Louisiana coasts, as well as South Florida and the
Keys this afternoon into Saturday night.

...Discussion...

Strong midlevel height falls will spread across the Ohio
Valley/Middle Atlantic during the day1 period as a pronounced upper
trough digs across the Great Lakes/OH Valley. This evolution
warrants surface pressures rising across the interior CONUS east of
the Rockies, ultimately forcing a cold front toward the upper TX/LA
Coast by the end of the period. Prior to the frontal passage, weak
low-level warm advection will aid some convective threat due in part
to the influence of a low-amplitude short-wave trough that will
eject across the western Gulf basin. Otherwise, lightning may
accompany frontal convection as the wind shift surges into this
region. In addition to isolated thunderstorms across the upper
TX/LA Coasts, moisture/buoyancy is expected to gradually advance
north across the FL Keys into the southern FL Peninsula. Weak
disturbance should encourage isolated thunderstorm development
across this region as well. In both scenarios, severe threat appears negligible.

..Darrow/Wendt.. 12/13/2025

$$

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ACUS01 KWNS 131242
SWODY1
SPC AC 131240

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0640 AM CST Sat Dec 13 2025

Valid 131300Z - 141200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today or tonight.

...Discussion...
Large-scale trough amplification will occur over the Midwest/East
through tonight, with expanding surface high pressure across the
Plains and Midwest in the wake of a cold front progressing
south-southeastward toward the Lower Mississippi Valley and Gulf
Coast by late tonight and early Sunday. Preceding the front, weak
warm/moist advection should allow for northeastward-expanding
thunderstorm development across southeast Texas and Louisiana today,
with potential persisting until the frontal passage tonight.

A low-latitude disturbance crossing the Gulf and a northward
moisture flux ahead of it will contribute to thunderstorm potential
across the Florida Keys/Florida Straits today, and also across the
southern Florida Peninsula tonight. Severe thunderstorms are
unlikely with these scenarios.

..Guyer/Lyons.. 12/13/2025

$$

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ACUS01 KWNS 131605
SWODY1
SPC AC 131604

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1004 AM CST Sat Dec 13 2025

Valid 131630Z - 141200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today or tonight.

...Southeast TX/Southwest LA...
Morning satellite loops confirm northward transport of low-level
moisture into parts of the southern Plains and lower MS Valley.
This trend will continue this afternoon and evening as a shallow
surface cold front sags southward through the region. Model
guidance suggests that weak but sufficient instability will develop
after dark from southeast TX into southwest LA to result in a few
pre-frontal thunderstorms. Shear is weak, and limited CAPE will
preclude organized severe storms. However, small hail is possible
in the strongest cores tonight.

...FL...
A low-latitude disturbance crossing the Gulf and a northward
moisture flux ahead of it will contribute to thunderstorm potential
across the Florida Keys/Florida Straits today, and also across the
southern Florida Peninsula tonight. Severe thunderstorms are
unlikely with these scenarios.

..Hart/Dean.. 12/13/2025

$$

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ACUS01 KWNS 131949
SWODY1
SPC AC 131948

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0148 PM CST Sat Dec 13 2025

Valid 132000Z - 141200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today or tonight.

...20z Update...
The previous forecast remains on track with only minor adjustments
may to the thunder line along the southern TX Gulf Coast where a
cold pool associated with offshore convection is spreading onshore. Thunderstorm coverage is still expected to increase later this afternoon/evening across southeast TX and southern LA, but the
potential for severe thunderstorms remains limited.

..Moore.. 12/13/2025

.PREV DISCUSSION... /ISSUED 1004 AM CST Sat Dec 13 2025/

...Southeast TX/Southwest LA...
Morning satellite loops confirm northward transport of low-level
moisture into parts of the southern Plains and lower MS Valley.
This trend will continue this afternoon and evening as a shallow
surface cold front sags southward through the region. Model
guidance suggests that weak but sufficient instability will develop
after dark from southeast TX into southwest LA to result in a few
pre-frontal thunderstorms. Shear is weak, and limited CAPE will
preclude organized severe storms. However, small hail is possible
in the strongest cores tonight.

...FL...
A low-latitude disturbance crossing the Gulf and a northward
moisture flux ahead of it will contribute to thunderstorm potential
across the Florida Keys/Florida Straits today, and also across the
southern Florida Peninsula tonight. Severe thunderstorms are
unlikely with these scenarios.

$$

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ACUS01 KWNS 140041
SWODY1
SPC AC 140039

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0639 PM CST Sat Dec 13 2025

Valid 140100Z - 141200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected tonight.

...01z Update...

Surface front has surged into central TX, arcing across northern LA
into central MS early this evening. Isolated thunderstorms have
developed ahead of this boundary over east TX and across northern
IL. This activity should gradually increase in areal coverage as the
front advances toward the northwest Gulf Coast. 00z soundings from
SHV and LCH exhibit sufficient buoyancy for lighting within deep
convection, but profiles do not favor particularly robust
thunderstorms and severe is not anticipated.

Scattered-numerous thunderstorm clusters are currently noted across
the FL Straits within a seasonally high PW air mass characterized by
weak buoyancy. Early-evening water-vapor imagery depicts a notable
short-wave trough over the eastern Gulf Basin. This feature should
continue to support convection across the Straits and the southern
FL Peninsula tonight.

..Darrow.. 12/14/2025

$$

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* Origin: Capitol City Online (1:2320/105)

ACUS01 KWNS 140520
SWODY1
SPC AC 140518

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1118 PM CST Sat Dec 13 2025

Valid 141200Z - 151200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few storms are possible across South Florida and the Florida Keys,
as well as the western Gulf Coast today.

...Discussion...

Strong upper trough over the Great Lakes/Midwest region will advance
off the Middle Atlantic Coast by 15/06z as the primary midlevel
speed max translate well downstream. Dominant surface anticyclone
will settle into the mid MS/OH Valley region by late afternoon which
will effectively drive the cold front deep into Mexico and across
the southern FL Peninsula. Early in the period, isolated
thunderstorms may be noted along the trailing cold front across the northwestern Gulf Coast region. Some risk for a few flashes of
lighting are also possible with weak convection across the southern
FL Peninsula before flow veers and stronger convergence shifts
offshore.

..Darrow/Wendt.. 12/14/2025

$$

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ACUS01 KWNS 141254
SWODY1
SPC AC 141252

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0652 AM CST Sun Dec 14 2025

Valid 141300Z - 151200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today or tonight.

...Discussion...
A prominent upper trough will continue to spread southeastward from
the Midwest/Great Lakes toward the Mid-Atlantic/Northeast coast by
tonight. Surface high pressure and related cold/dry continental
trajectories will be increasingly prevalent east of the Rockies.
Near a south/southeastward-advancing cold front, isolated
thunderstorms will remain possible early today over the northwest
Gulf, while a few flashes of lighting are also possible with weak
convection across the southern Florida Peninsula, before flow veers
and stronger convergence shifts offshore. Lastly, a few lightning
flashes could also occur late tonight near coastal Washington within
the warm/moist conveyor preceding an approaching shortwave trough
and cold front.

..Guyer/Lyons.. 12/14/2025

$$

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ACUS01 KWNS 141555
SWODY1
SPC AC 141554

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0954 AM CST Sun Dec 14 2025

Valid 141630Z - 151200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today or tonight.

Dry and stable conditions will prevail over most of the CONUS today,
with a few small exceptions. A strong cold front sagging southward
across TX might result in isolated afternoon thunderstorms over
south TX. Widely scattered showers and thunderstorms could affect
south FL this afternoon as the same front weakens and approaches the
area. And finally, a few lightning strikes could occur inland
across western WA late tonight as a strong shortwave trough
approaches. No severe storms are anticipated in any of these areas.

..Hart/Weinman.. 12/14/2025

$$

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ACUS01 KWNS 141944
SWODY1
SPC AC 141942

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0142 PM CST Sun Dec 14 2025

Valid 142000Z - 151200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today or tonight.

...20z Update...

The 10 percent thunder area was removed from South TX as the surface
front has surged south of the area into northeast Mexico. A minor
southward adjustment was also made across South Florida based on
latest surface observations and radar trends. Isolated weak
thunderstorms may persist the remainder of the afternoon from South
FL into the Keys.

..Leitman.. 12/14/2025

.PREV DISCUSSION... /ISSUED 0954 AM CST Sun Dec 14 2025/

Dry and stable conditions will prevail over most of the CONUS today,
with a few small exceptions. A strong cold front sagging southward
across TX might result in isolated afternoon thunderstorms over
south TX. Widely scattered showers and thunderstorms could affect
south FL this afternoon as the same front weakens and approaches the
area. And finally, a few lightning strikes could occur inland
across western WA late tonight as a strong shortwave trough
approaches. No severe storms are anticipated in any of these areas.

$$

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ACUS01 KWNS 150033
SWODY1
SPC AC 150032

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0632 PM CST Sun Dec 14 2025

Valid 150100Z - 151200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected tonight.

...01z Update...

Northwesterly flow is deepening across the southern FL Peninsula as
the primary synoptic front surges toward the FL Straits. Isolated
showers are lingering across this region, with even a few flashes of
lightning near West Palm Beach. However, this activity should
continue to wane then focus well offshore over the next few hours.

00z sounding from UIL is quite stable this evening with poor lapse
rates noted through 6km. Late tonight elevated buoyancy may increase
near the WA coast such that weak convection is able to develop ahead
of approaching short-wave trough. If lightning is noted with this
activity it will remain quite sparse.

..Darrow.. 12/15/2025

$$

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ACUS01 KWNS 150528
SWODY1
SPC AC 150527

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1127 PM CST Sun Dec 14 2025

Valid 151200Z - 161200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorm probabilities are low today.

...Pacific Northwest...

100+kt 500mb speed max is forecast to translate inland along the
WA/OR coast around 16/00z. Low-amplitude short-wave trough will
induce strong height falls near the international border ahead of
this feature, coincident with a notable surface front that will
surge inland after 21z. While profiles will cool and steepen at
midlevels, forecast soundings are not particularly buoyant either
side of the trough, and the prospect for deep convection capable of
generating lightning appears low. While the thunderstorm potential
appears low, weak midlevel convection is possible and a flash or two
can not be ruled out. This, however, does not warrant a categorical
risk for thunderstorms during the day1 period.

..Darrow/Wendt.. 12/15/2025

$$

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ACUS01 KWNS 151245
SWODY1
SPC AC 151244

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0644 AM CST Mon Dec 15 2025

Valid 151300Z - 161200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today or tonight.

...Discussion...
A progressive shortwave trough and a 100+ kt mid-level speed max
will progress eastward and inland across Washington/British Columbia
by later this afternoon and evening. A few lightning flashes could
occur for coastal areas of the Pacific Northwest relatively early
today via weak elevated buoyancy within the warm conveyor preceding
the shortwave trough/cold front. Mid-level temperatures will
subsequently cool in the post-frontal environment, but the potential
for sufficiently deep convection through lightning-conducive levels/temperatures should remain marginal later today, thus
limiting thunderstorm potential.

..Guyer/Lyons.. 12/15/2025

$$

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ACUS01 KWNS 151604
SWODY1
SPC AC 151603

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1003 AM CST Mon Dec 15 2025

Valid 151630Z - 161200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today or tonight.

...Synopsis...

Thunderstorm potential will remain low today as strong surface high
pressure and cut-off Gulf moisture results in a dry/stable airmass
across much of the CONUS. A weak shortwave impulse will move over
portions of the Pacific Northwest today/tonight. A few lightning
flashes will be possible offshore, but minimal instability and
generally shallow convection will preclude stronger updrafts through sufficiently cold temperatures aloft to produce thunderstorms
inland.

..Leitman.. 12/15/2025

$$

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ACUS01 KWNS 151933
SWODY1
SPC AC 151931

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0131 PM CST Mon Dec 15 2025

Valid 152000Z - 161200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today or tonight.

...20z Update...
No changes are needed to the current D1 Convective Outlook. See
previous discussion below for more information.

..Thornton.. 12/15/2025

.PREV DISCUSSION... /ISSUED 1003 AM CST Mon Dec 15 2025/

...Synopsis...

Thunderstorm potential will remain low today as strong surface high
pressure and cut-off Gulf moisture results in a dry/stable airmass
across much of the CONUS. A weak shortwave impulse will move over
portions of the Pacific Northwest today/tonight. A few lightning
flashes will be possible offshore, but minimal instability and
generally shallow convection will preclude stronger updrafts through sufficiently cold temperatures aloft to produce thunderstorms
inland.

$$

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ACUS01 KWNS 160058
SWODY1
SPC AC 160056

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0656 PM CST Mon Dec 15 2025

Valid 160100Z - 161200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast tonight.

...Pacific Northwest...
Thunderstorms earlier this afternoon over southwest OR have fully
decayed in the past couple hours. A lone storm or two will be
possible tonight within the persistent, but modest low-level warm
conveyor that will shift farther inland to the northern Rockies.
With flimsy elevated buoyancy expected (MUCAPE at or below 100
J/kg), overall thunderstorm probabilities appear negligible.

A few lightning flashes were also detected in the last hour across
northwest WA near a shortwave trough, that will rapidly progress
east across far southern AB/SK tonight. This thunder threat is
expected to remain very isolated and diminish east of the Cascades.

..Grams.. 12/16/2025

$$

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ACUS01 KWNS 160539
SWODY1
SPC AC 160537

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1137 PM CST Mon Dec 15 2025

Valid 161200Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE PACIFIC
NORTHWEST...

...SUMMARY...
Sporadic severe gusts may accompany isolated thunderstorms across
parts of the Pacific Northwest on Tuesday night.

...Pacific Northwest...
A vigorous shortwave trough will approach the Pacific Northwest
coast through tonight before shifting inland over WA during the
early morning Wednesday. A deepening surface cyclone will move
across southern BC towards southwest AB, with a Pacific cold front
trailing south-southwestward. Low-topped convection is expected to
accompany the front, initially approaching the WA coast by late
evening. Surface-based buoyancy will remain meager, but strong
gradient winds will shift from the southwest to west-northwest as
the front passes. Sporadic lightning flashes and strong to severe
gusts may accompany passage of this low-topped squall before it
subsides inland in western WA/OR.

Intense lower-level flow will likely peak in the overnight to early
morning hours. Buoyancy should remain quite limited along and east
of the Cascades, but most guidance indicates broken low-topped
convection should spread east along/ahead of the front amid
pronounced large-scale ascent. Background gradient winds will likely
be capable of producing severe gusts, and some of these may be
coincident with sporadic lightning flashes.

..Grams/Wendt.. 12/16/2025

$$

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ACUS01 KWNS 161247
SWODY1
SPC AC 161245

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0645 AM CST Tue Dec 16 2025

Valid 161300Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
PACIFIC NORTHWEST...

...SUMMARY...
Sporadic severe wind gusts may accompany isolated thunderstorms
across parts of the Pacific Northwest tonight.

...Pacific Northwest...
A vigorous lead shortwave trough will steadily amplify today and
reach the coastal Pacific Northwest tonight. This will be
accompanied by a strong deep-layer wind field, highlighted by 90+ kt
winds at 500 mb and 50-80 kt winds within the lowest 1-3 km AGL.
This will be as Pacific moisture also steadily increases tonight in
tandem with the inland-advancing cold front. Low-topped convection
is expected to accompany the front, initially approaching the
Washington coast by late evening, and then more interior areas
overnight/early Wednesday. Surface-based buoyancy will remain
meager, but very strong gradient winds will shift from the southwest
to west-northwest as the front passes. Sporadic lightning flashes
and strong to severe-caliber wind gusts may accompany the passage of
this low-topped convective line, with the most intense low-level winds/convective influences expected to peak during the overnight
and early morning hours of Wednesday.

..Guyer/Lyons.. 12/16/2025

$$

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ACUS01 KWNS 161622
SWODY1
SPC AC 161620

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1020 AM CST Tue Dec 16 2025

Valid 161630Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE PACIFIC NORTHWEST...

...SUMMARY...
Sporadic severe wind gusts may accompany low-topped convection
across parts of the Pacific Northwest tonight into early Wednesday
morning.

...Pacific Northwest...
A strong mid-level shortwave trough over the eastern Pacific will
amplify today and reach the coastal Pacific Northwest late tonight.
This trough will be accompanied by an enhanced deep-layer wind
field, with 90-100+ kt winds at 500 mb and around 50-80 kt flow in
the lowest 1-3 km AGL. Low-level moisture should also gradually
increase tonight ahead of an eastward-advancing cold front.
Low-topped convection may accompany the front, initially approaching
the WA Coast by late evening, and then more interior areas
overnight/early Wednesday.

Surface-based buoyancy will remain quite meager due to poor lapse
rates aloft and the time of night. Still, rather strong low-level
gradient winds will shift from the southwest to west-northwest as
the front passes. Sporadic lightning flashes and occasional strong
to severe-caliber wind gusts may accompany the passage of this
low-topped convective line, with the most intense low-level
winds/convective influences expected to peak during the overnight
and early morning hours Wednesday. However, it remains quite
uncertain if these convectively enhanced winds will be substantially
stronger than the background gradient wind field. Therefore, the
Marginal Risk has been maintained with no changes.

..Gleason/Weinman.. 12/16/2025

$$

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ACUS01 KWNS 161929
SWODY1
SPC AC 161927

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0127 PM CST Tue Dec 16 2025

Valid 162000Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE
PACIFIC NORTHWEST...

...SUMMARY...
Sporadic severe wind gusts may accompany low-topped convection
across parts of the Pacific Northwest tonight into early Wednesday
morning.

...20z Update...
No changes are needed to the D1 Convective Outlook. See previous
discussion for more information.

..Thornton.. 12/16/2025

.PREV DISCUSSION... /ISSUED 1020 AM CST Tue Dec 16 2025/

...Pacific Northwest...
A strong mid-level shortwave trough over the eastern Pacific will
amplify today and reach the coastal Pacific Northwest late tonight.
This trough will be accompanied by an enhanced deep-layer wind
field, with 90-100+ kt winds at 500 mb and around 50-80 kt flow in
the lowest 1-3 km AGL. Low-level moisture should also gradually
increase tonight ahead of an eastward-advancing cold front.
Low-topped convection may accompany the front, initially approaching
the WA Coast by late evening, and then more interior areas
overnight/early Wednesday.

Surface-based buoyancy will remain quite meager due to poor lapse
rates aloft and the time of night. Still, rather strong low-level
gradient winds will shift from the southwest to west-northwest as
the front passes. Sporadic lightning flashes and occasional strong
to severe-caliber wind gusts may accompany the passage of this
low-topped convective line, with the most intense low-level
winds/convective influences expected to peak during the overnight
and early morning hours Wednesday. However, it remains quite
uncertain if these convectively enhanced winds will be substantially
stronger than the background gradient wind field. Therefore, the
Marginal Risk has been maintained with no changes.

$$

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ACUS01 KWNS 170050
SWODY1
SPC AC 170048

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0648 PM CST Tue Dec 16 2025

Valid 170100Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE PACIFIC
NORTHWEST...

...SUMMARY...
Sporadic severe gusts may accompany low-topped convection across
parts of the Pacific Northwest tonight into early Wednesday morning.

...Pacific Northwest...
A vigorous shortwave trough will reach coastal WA by late tonight
and spread inland through 12Z Wednesday. This trough will be
accompanied by an intense tropospheric wind field, characterized by
70-90 kts at 700 mb, that will spread across WA and OR during
06-12Z. A surface cyclone will move onshore in BC and occlude, as
downstream lee cyclogenesis occurs over southern AB.

Low-topped convection is expected to increase along the trailing
cold front attendant to the occluded cyclone, initially reaching
coastal WA towards 06Z. Surface-based buoyancy will be scant along
the front, but sporadic lightning flashes and occasional strong to severe-caliber wind gusts may accompany the passage of this
low-topped convective line. Low-topped convection should also
increase ahead of this line overnight, as strong large-scale ascent
coincides with peak low to mid-level flow. With minimal instability,
low confidence exists in the degree of convective enhancement beyond
the gradient winds. Thus, the level 1-MRGL risk has been maintained
with no changes.

..Grams.. 12/17/2025

$$

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ACUS01 KWNS 170547
SWODY1
SPC AC 170545

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1145 PM CST Tue Dec 16 2025

Valid 171200Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE NORTHWEST...

...SUMMARY...
Sporadic severe gusts may accompany low-topped convection across
parts of the Northwest this morning into midday.

...Northwest...
A vigorous shortwave trough will move quickly east along the
Canadian border from WA to the northern Great Plains by evening.
Intense tropospheric flow will accompany this wave, yielding
widespread high winds across much of the Northwest to the northern
Great Plains. Deep lee surface cyclone over southern AB should reach
the Red River Valley of the North. Attendant Pacific cold front will
sweep east with a tight pressure gradient in its wake.

Low-topped convection may be ongoing at 12Z along the Columbia Basin
portion of the front. Most guidance also suggests an increase in
low-topped convection should occur towards late morning across parts
of the Snake River Plain as the front pushes east. Surface-based
instability will remain scant in both regimes with morning
temperatures in the 40s to low 50s. Despite the cool temperatures,
this may be sufficient for sporadic lightning flashes amid strong
large-scale ascent. With very strong surface winds accompanying the
front, both regimes could be coincident with severe wind gusts.

The bulk of sustained severe wind speeds should become primarily
confined along/east of the Rockies in MT to the CO Front Range this
afternoon per HREF/REFS guidance. However, potential for severe
convective gusts appears too conditional with negligible
surface-based buoyancy anticipated.

..Grams/Wendt.. 12/17/2025

$$

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ACUS01 KWNS 171257
SWODY1
SPC AC 171255

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0655 AM CST Wed Dec 17 2025

Valid 171300Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHWEST AND NORTHERN INTERMOUNTAIN REGION...

...SUMMARY...
Sporadic severe wind gusts may accompany low-topped convection
across parts of the Northwest and northern Intermountain region this
morning into midday.

...Northwest/Northern Intermountain region...
A progressive/vigorous shortwave trough will continue to modestly
amplify and otherwise race east-southeastward from the
Washington/British Columbia border vicinity this morning to the
northern Plains tonight. Intense deep-tropospheric flow (highlighted
by 55-85 kt at 700 mb) will accompany this wave, yielding widespread
high winds across much of the Northwest to the northern Great
Plains.

Low-topped convection, occasionally capable of lightning and
semi-organized line segments, will continue in association with the east/southeastward-advancing cold front, with convection potentially
expanding by late morning towards the Snake River Plain/Yellowstone
vicinity and potentially other parts of the northeast Great Basin by
afternoon. Surface-based instability will be very limited, but some convectively enhanced wind gusts may occur.

..Guyer/Lyons.. 12/17/2025

$$

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ACUS01 KWNS 171624
SWODY1
SPC AC 171622

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1022 AM CST Wed Dec 17 2025

Valid 171630Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTHERN IDAHO AND NORTHERN UTAH...

...SUMMARY...
While strong to locally severe winds may occur with low-topped
convection through early afternoon across parts of southern Idaho
and northern Utah, the overall threat for organized severe
thunderstorms appears low.

...Interior Northwest and Northern Great Basin/Rockies...
A powerful mid-level shortwave trough and associated sub-980 mb
surface low will move quickly eastward today across the interior Northwest/northern Rockies and adjacent western Canada. A strong
surface cold front will likewise translate east-southeastward over
the northern Intermountain/Great Basin region late this morning into
the afternoon. Widespread cloud cover remains prevalent ahead of the
front across southern ID into northern UT and vicinity, with cool
surface temperatures and very limited low-level moisture also
present. MUCAPE is expected to remain only barely sufficient to
support convection. But, given the enhanced flow at low levels noted
on recent VWPs from KCBX/KSFX, it is not entirely out of the
question that convectively augmented gusts may exceed the already
strong background gradient winds on a localized basis. The Marginal
Risk has therefore been maintained for parts of southern ID/northern
UT and vicinity, even though the overall threat for organized severe thunderstorms will remain low.

..Gleason/Weinman.. 12/17/2025

$$

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ACUS01 KWNS 171949
SWODY1
SPC AC 171947

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0147 PM CST Wed Dec 17 2025

Valid 172000Z - 181200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms will continue across portions of the Intermountain
West and Texas/Louisiana coasts through this evening. The overall
threat for organized severe thunderstorms appears low.

...20z Update...
The Marginal Risk across southern Idaho/northern Utah has been
removed with this outlook. Thunderstorm activity has shown gradual
weakening with only meager MLCAPE remaining. Occasional strong
gradient winds will continue with the upper-level wave but the
overall convective severe threat appears to be waning.

..Thornton.. 12/17/2025

.PREV DISCUSSION... /ISSUED 1022 AM CST Wed Dec 17 2025/

...Interior Northwest and Northern Great Basin/Rockies...
A powerful mid-level shortwave trough and associated sub-980 mb
surface low will move quickly eastward today across the interior Northwest/northern Rockies and adjacent western Canada. A strong
surface cold front will likewise translate east-southeastward over
the northern Intermountain/Great Basin region late this morning into
the afternoon. Widespread cloud cover remains prevalent ahead of the
front across southern ID into northern UT and vicinity, with cool
surface temperatures and very limited low-level moisture also
present. MUCAPE is expected to remain only barely sufficient to
support convection. But, given the enhanced flow at low levels noted
on recent VWPs from KCBX/KSFX, it is not entirely out of the
question that convectively augmented gusts may exceed the already
strong background gradient winds on a localized basis. The Marginal
Risk has therefore been maintained for parts of southern ID/northern
UT and vicinity, even though the overall threat for organized severe thunderstorms will remain low.

$$

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ACUS01 KWNS 180023
SWODY1
SPC AC 180021

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0621 PM CST Wed Dec 17 2025

Valid 180100Z - 181200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible along portions of the TX/LA Gulf
coasts tonight.

...01z Update...

Weak, southern-stream short-wave trough is advancing off the south
TX coast early this evening. A few thunderstorms linger near the
center of a weak midlevel circulation around the Corpus Christi
region; however, the most concentrated deep convection is now
focused offshore and should continue to be shunted east ahead of the
short wave.

Isolated thunderstorms may eventually develop ahead of this feature
downstream across southeast LA later tonight, but negligible
buoyancy currently exists on the 00z sounding from LIX. By the end
of the period, adequate destabilization should materialize across
this region such that lightning is possible with deep convection,
primarily after 08-09z.

..Darrow.. 12/18/2025

$$

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ACUS01 KWNS 180540
SWODY1
SPC AC 180538

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1138 PM CST Wed Dec 17 2025

Valid 181200Z - 191200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe potential will be limited today, but isolated strong wind
gusts are possible across portions of the Lower Ohio and Tennessee
Valleys.

...Lower Ohio/TN Valleys...

Strong midlevel trough is advancing quickly across the
northern/central High Plains late this evening. This feature is
forecast to progress into the MS Valley by late afternoon then eject negative-tilt into the OH Valley during the overnight period.
Intense 12hr height falls, on the order of 210m, will spread across
the OH Valley and this is expected to aid large-scale forcing along
a sharp cold front that will surge into IN/KY/TN by 19/00z. Poor destabilization is expected ahead of the front and forecast
soundings exhibit meager instability, and this is mostly with an
elevated parcel. While buoyancy will be weak, a strongly forced band
of frontal convection is expected to develop and spread east. Given
the level of parcel ascent, current thinking is a stable boundary
layer will minimize the risk of severe gusts near the surface. Even
so, isolated strong winds may accompany some portions of the
convective line, but the risk of severe gusts in excess of 50kt
appears too low to warrant a MRGL risk at this time.

..Darrow/Wendt.. 12/18/2025

$$

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ACUS01 KWNS 181302
SWODY1
SPC AC 181300

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0700 AM CST Thu Dec 18 2025

Valid 181300Z - 191200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS COASTAL
NORTH CAROLINA...

...SUMMARY...
While organized severe potential may be limited today, isolated
strong wind gusts may occur across portions of the Lower Ohio and
Tennessee Valleys this afternoon and evening and/or across the
Carolinas late tonight.

...Tennessee Valley/Lower Ohio Valley...
A prominent upper-level trough centered over the northern
Plains/Upper Midwest early this morning will continue to amplify and
spread east-southeastward, taking on a more negative tilt tonight
over the Midwest/Cumberland Plateau with intense 12-hr height falls
on the order of 210m. A robust low/mid-level wind field will
accompany this trough, especially into tonight with 60-80 kt winds
within the lowest 1-3km AGL coincident with the modifying warm
sector. But, only limited destabilization is expected ahead of the
front, with forecast soundings generally exhibiting meager
instability. While buoyancy will be weak, a strongly forced band of
frontal convection is expected to develop and spread eastward later
this afternoon into evening. Current thinking is a stable boundary
layer will minimize the risk of severe wind gusts near the surface,
but somewhat taller/more sustained storms could occur across the
Tennessee Valley including Middle/eastern Tennessee and much of
Alabama into parts of Georgia, with at least some convectively
enhanced wind gust potential, possibly to near-severe levels.

...Carolinas...
Some strong/locally severe storms could occur late tonight through
the predawn/early morning hours of Friday, attributable to an
increasingly negative-tilt upper-level trough and a related robust strengthening of the deep-layer wind field. The abatement and
modification of continental/cold air inland is a key uncertainty,
and some guidance such as 00z/06z NAM, may be a bit too aggressive,
albeit modest/weak overall, regarding late-night near-surface-based destabilization. Primary concern is for the immediate coastal
areas/Outer Banks where somewhat greater airmass
modification/low-level moistening is more plausible. But it is also
possible that convectively enhanced wind gusts materialize inland
(including Piedmont areas) in the predawn hours..

..Guyer/Lyons.. 12/18/2025

$$

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ACUS01 KWNS 181633
SWODY1
SPC AC 181631

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1031 AM CST Thu Dec 18 2025

Valid 181630Z - 191200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MISSISSIPPI/TENNESSEE/LOWER OHIO VALLEYS...AND PORTIONS OF
COASTAL NORTH CAROLINA...

...SUMMARY...
Isolated strong to severe thunderstorms capable of producing
occasional damaging winds and perhaps a tornado or two may occur
through this evening across parts of the lower/mid Mississippi
Valley into the Tennessee Valley/Southeast, and late tonight across
portions of coastal North Carolina.

...Tennessee Valley/Lower Ohio Valley into the Southeast...
A pronounced mid/upper-level shortwave trough with attendant 70-90
kt mid-level jet will advance quickly eastward today across the
Upper Midwest into the MS/OH/TN Valleys. An associated deep surface
low over northern MN this morning is forecast to continue developing northeastward into Ontario/Quebec through tonight, with a trailing
cold front forecast to sweep east-southeastward over much of the
mid/lower MS Valley into the OH/TN Valleys and Southeast. Low-level
moisture return ahead of the cold front remains quite limited,
except for parts of MS/AL where low to mid 60s surface dewpoints are
beginning to spread inland. Even so, wind fields remain quite
favorable for thunderstorm organization, with ample low-level and
deep-layer shear present. Current expectations are for a low-topped
line of convection to further develop along the cold front through
this afternoon/evening. Although instability is expected to remain
minimal with northward extent into the OH/TN Valleys, there is still
potential for strong to severe gusts that will be convectively
enhanced beyond the already strong background gradient wind field.
Some chance for a tornado may also exist across parts of MS/AL where
greater instability/low-level moisture will reside. Given latest
observational and guidance trends, a Marginal Risk has been included
where the best potential for occasional strong to damaging winds is
apparent.

...Coastal North Carolina...
Isolated strong to locally severe convection may occur late tonight
through early Friday morning as an increasingly negative-tilt
mid-level trough and a related robust strengthening of the
deep-layer wind field approach eastern NC. The gradual modification
and erosion of continental/cold air is a key uncertainty due to
persistent surface high pressure along the East Coast into western
Atlantic. Some guidance such as the 12Z NAM may be a bit too
aggressive regarding late-night near-surface-based destabilization.
Still, the main area of concern is for the immediate NC coastal
areas/Outer Banks, where somewhat greater airmass
modification/low-level moistening should occur amid strong low-level
and deep-layer shear. If surface-based thunderstorms can form and
spread northeastward across this area, they could pose a threat for
isolated severe/damaging winds and perhaps a tornado. But, it is
also possible that convectively enhanced wind gusts materialize
inland (including Piedmont areas) in the predawn hours, although
confidence in this occurring remains low.

..Gleason/Weinman.. 12/18/2025

$$

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ACUS01 KWNS 182002
SWODY1
SPC AC 182000

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0200 PM CST Thu Dec 18 2025

Valid 182000Z - 191200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MS/TN/OH VALLEYS INTO THE SOUTHEAST...AND ALSO ACROSS COASTAL
NC...

...SUMMARY...
Isolated strong to severe thunderstorms capable of producing
occasional damaging winds and perhaps a tornado or two may occur
through this evening across parts of the lower/mid Mississippi
Valley into the Tennessee and Ohio Valleys and Southeast, and late
tonight across portions of coastal North Carolina.

...MS/OH/TN Valleys into the Southeast...
The primary changes to the Marginal Risk have been to clear areas
behind the low-topped convective line and cold front, and to expand northeastward somewhat based on where recent HRRR/RRFS guidance
maintains a low-topped but well-defined frontal band with potential
for localized strong/damaging gusts.

A line of low-topped convection has developed along a cold front and
is moving eastward across parts of IL and southeast MO this
afternoon. Despite very weak to negligible buoyancy, very strong
low-level flow/shear (with 50+ kt at 1 km AGL per regional VWPs) has
supported occasional gusts of 40-55 mph and isolated wind-damage
reports along this line. Forcing related to a strong mid/upper-level
shortwave trough moving quickly eastward across the region will help
to sustain a low-topped frontal band into this evening, which may be
capable of producing sporadic strong/damaging gusts into parts of
the Ohio Valley.

Recent HRRR/RRFS runs suggest that gusty winds associated with the
frontal band may spread across parts of the Allegheny Plateau
overnight, but with essentially nil buoyancy expected in this area,
confidence is currently too low to expand wind probabilities into
this area.

Farther south into parts of TN/MS/AL, somewhat greater (though still
weak) buoyancy will be in place later this afternoon into the early
evening, as 60s F dewpoints spread northward to near the TN/MS/AL
border region. A broken band of storms may develop in advance of the
front, with potential for at least marginal supercell structures and
an attendant threat of isolated damaging wind and possibly a
tornado. Any longer-lived cells may tend to merge into the
eastward-moving frontal band with time, with at least an isolated
severe threat spreading east across TN through the evening.

...Coastal NC...
No major changes have been made to the Marginal Risk across coastal
NC. See the previous discussion below for more information.

...FL Panhandle vicinity...
Cells with occasional rotation have been noted offshore of the FL
Panhandle this afternoon, though temperatures remain relatively cool
with widespread cloudiness inland. There is some potential for a
stronger cell or two to eventually approach the coast or develop
slightly inland, but lingering near-surface stability may tend to
limit the severe threat across this area.

..Dean.. 12/18/2025

.PREV DISCUSSION... /ISSUED 1031 AM CST Thu Dec 18 2025/

...Tennessee Valley/Lower Ohio Valley into the Southeast...
A pronounced mid/upper-level shortwave trough with attendant 70-90
kt mid-level jet will advance quickly eastward today across the
Upper Midwest into the MS/OH/TN Valleys. An associated deep surface
low over northern MN this morning is forecast to continue developing northeastward into Ontario/Quebec through tonight, with a trailing
cold front forecast to sweep east-southeastward over much of the
mid/lower MS Valley into the OH/TN Valleys and Southeast. Low-level
moisture return ahead of the cold front remains quite limited,
except for parts of MS/AL where low to mid 60s surface dewpoints are
beginning to spread inland. Even so, wind fields remain quite
favorable for thunderstorm organization, with ample low-level and
deep-layer shear present. Current expectations are for a low-topped
line of convection to further develop along the cold front through
this afternoon/evening. Although instability is expected to remain
minimal with northward extent into the OH/TN Valleys, there is still
potential for strong to severe gusts that will be convectively
enhanced beyond the already strong background gradient wind field.
Some chance for a tornado may also exist across parts of MS/AL where
greater instability/low-level moisture will reside. Given latest
observational and guidance trends, a Marginal Risk has been included
where the best potential for occasional strong to damaging winds is
apparent.

...Coastal North Carolina...
Isolated strong to locally severe convection may occur late tonight
through early Friday morning as an increasingly negative-tilt
mid-level trough and a related robust strengthening of the
deep-layer wind field approach eastern NC. The gradual modification
and erosion of continental/cold air is a key uncertainty due to
persistent surface high pressure along the East Coast into western
Atlantic. Some guidance such as the 12Z NAM may be a bit too
aggressive regarding late-night near-surface-based destabilization.
Still, the main area of concern is for the immediate NC coastal
areas/Outer Banks, where somewhat greater airmass
modification/low-level moistening should occur amid strong low-level
and deep-layer shear. If surface-based thunderstorms can form and
spread northeastward across this area, they could pose a threat for
isolated severe/damaging winds and perhaps a tornado. But, it is
also possible that convectively enhanced wind gusts materialize
inland (including Piedmont areas) in the predawn hours, although
confidence in this occurring remains low.

$$

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ACUS01 KWNS 190057
SWODY1
SPC AC 190056

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0656 PM CST Thu Dec 18 2025

Valid 190100Z - 191200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE LOWER MISSISSIPPI VALLEY TO THE OHIO VALLEY...

...SUMMARY...
Isolated strong to severe thunderstorms capable of producing
occasional damaging winds, and perhaps a tornado or two, remain
possible this evening across parts of the lower/mid Mississippi
Valley into the Tennessee and Ohio Valleys and Southeast, and late
tonight across portions of coastal North Carolina.

...01z Update...

Strong midlevel trough is advancing across the MS Valley early this
evening. Associated pronounced surface front has surged into
southeast MI-western KY-northwest MS. This boundary will shift
across much of the OH/TN Valleys by late evening as the dynamic
trough induces strong height falls across this region. Latest radar
data reflects this with a strongly forced line of frontal
convection. A few strong gusts have been reported along the northern
sections of this linear MCS. Of potentially more concern is
convection that has developed ahead of the front across eastern MS
into northwest AL. This activity has evolved within a greater
buoyancy air mass characterized by SBCAPE on the order of 500-1000
J/kg. Lower 60s surface dew points have contributed to this
instability and a few supercells have matured and are advancing east
across Tornado Watch #0642. Greatest risk for organized severe will
remain focused across the northern Gulf states this evening.
Damaging winds, along with some tornado risk continues.

Risk of severe will increase late tonight near the Outer Banks
region of NC, and for this region will maintain MRGL Risk.

..Darrow.. 12/19/2025

$$

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ACUS01 KWNS 190530
SWODY1
SPC AC 190529

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1129 PM CST Thu Dec 18 2025

Valid 191200Z - 201200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE MID ATLANTIC...

...SUMMARY...
Isolated damaging winds may accompany convection over the Mid
Atlantic today.

...Mid Atlantic...

Late-evening water-vapor imagery depicts a notable midlevel trough
over the MS Valley, shifting east in line with latest model
guidance. This feature is forecast to take a more negative-tilt
orientation by late morning as 100+kt 500mb speed max
develops/translates across the Mid Atlantic by 18z. Impressive 12hr
height falls at 500mb will overspread the OH Valley into New England
where values will range from 240-300m in response to this strong
feature. Needless to say, very strong wind fields will provide
background support for organized frontal convection. HREF guidance
is in general agreement that a narrow strongly forced line of
convection will develop along the surging cold front early in the
period. Forecast soundings do not exhibit more than weak SBCAPE with
this frontal convection, but some mixing is expected given that
0-3km lapse rates should be on the order of 7 C/km. 40kt mean wind
within this layer is expected to contribute to gusty winds with this
activity. Have introduced MRGL Risk of damaging winds to account for
strong gusts with a narrow line of convection that will surge east
along the front.

Given the limited buoyancy across southern New England will not
introduce wind probabilities at this time.

..Darrow/Squitieri.. 12/19/2025

$$

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ACUS01 KWNS 191255
SWODY1
SPC AC 191254

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0654 AM CST Fri Dec 19 2025

Valid 191300Z - 201200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE MID-ATLANTIC/NORTHEAST STATES...

...SUMMARY...
Isolated damaging winds may accompany convection across the Mid-Atlantic/Northeast today.

...North Carolina and Mid-Atlantic/Northeast States...
A prominent upper-level trough centered over the Great Lakes/Ohio
Valley will continue to take on a negative tilt as it quickly
transitions east-northeastward toward New England the Canadian
Maritimes tonight. A very strong deep-layer wind field (80-110 kt at
500 mb) is attendant to this trough, with these strong winds aloft
partially overlapping a modestly moist/minimally unstable warm
sector along the I-95 corridor/East Coast ahead of an
eastward-advancing cold front. A strongly forced semi-organized
low-topped convective line, with little or no lightning flashes, is
ongoing around sunrise across northeast North Carolina and southeast
Virginia, and this may further develop north-northeastward across
additional portions of the Mid-Atlantic region this morning. Even
with minimal buoyancy, some stronger/locally severe wind gusts could
occur this morning, and possibly through early afternoon across
parts of the near-coastal Northeast.

..Guyer/Marsh.. 12/19/2025

$$

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ACUS01 KWNS 191621
SWODY1
SPC AC 191620

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1020 AM CST Fri Dec 19 2025

Valid 191630Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
While strong/gusty winds will continue across the Mid-Atlantic and
Northeast today, the threat for organized severe thunderstorms is
expected to remain low.

...Mid-Atlantic/Northeast...
A pronounced mid/upper-level trough with very strong low/mid-level
flow will continue moving east-northeastward today across the
Mid-Atlantic and Northeast. Associated surface cold front will
likewise develop eastward across these regions through the
afternoon, and will clear the Atlantic Coast by this evening. A
loosely organized, low-topped convective line has moved east of NJ,
and should impact parts of Long Island over the next couple of
hours. Due to poor lapse rates aloft and limited diurnal heating
with continued cloud cover, minimal instability is forecast to be in
place ahead of this line. The threat for strong/gusty winds should
continue both with gradient winds within the strong low-level warm
advection regime and along/behind the front. But given the poor
thermodynamic environment and tendency for any additional convection
to remain elevated, the Marginal Risk across the
Mid-Atlantic/Northeast has been removed with this update.

..Gleason/Hart.. 12/19/2025

$$

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ACUS01 KWNS 192001
SWODY1
SPC AC 191959

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0159 PM CST Fri Dec 19 2025

Valid 192000Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
While strong/gusty winds remain possible across the Mid-Atlantic and
Northeast this afternoon and evening, the threat for organized
severe thunderstorms is expected to remain low.

...20Z Update...
Only minor changes have been made to the existing General
Thunderstorm areas. A band of low-topped convection is moving across
eastern PA toward northern NJ this afternoon, with sporadic strong
to severe gusts noted with this feature. Organized convection is not
expected due to negligible buoyancy, but strong deep-layer winds
associated with a powerful mid/upper-level trough and attendant cold
front moving across the eastern CONUS will continue to support
strong/damaging gusts both near and removed from any remaining
convection.

..Dean.. 12/19/2025

.PREV DISCUSSION... /ISSUED 1020 AM CST Fri Dec 19 2025/

...Mid-Atlantic/Northeast...
A pronounced mid/upper-level trough with very strong low/mid-level
flow will continue moving east-northeastward today across the
Mid-Atlantic and Northeast. Associated surface cold front will
likewise develop eastward across these regions through the
afternoon, and will clear the Atlantic Coast by this evening. A
loosely organized, low-topped convective line has moved east of NJ,
and should impact parts of Long Island over the next couple of
hours. Due to poor lapse rates aloft and limited diurnal heating
with continued cloud cover, minimal instability is forecast to be in
place ahead of this line. The threat for strong/gusty winds should
continue both with gradient winds within the strong low-level warm
advection regime and along/behind the front. But given the poor
thermodynamic environment and tendency for any additional convection
to remain elevated, the Marginal Risk across the
Mid-Atlantic/Northeast has been removed with this update.

$$

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ACUS01 KWNS 200020
SWODY1
SPC AC 200018

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0618 PM CST Fri Dec 19 2025

Valid 200100Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected through tonight.

...Synopsis...
A mid-level trough and accompanying surface trough are ejecting into
the Atlantic, with any available scant buoyancy being displaced east
of the CONUS. As such, any thunderstorms and accompanying
thunderstorm wind threat should be ending soon, though damaging
gusts from gradient flow (non-thunderstorm processes) may persist
through the evening hours. Elsewhere across the CONUS, a zonal upper
pattern will be in place, with a few embedded impulses poised to
traverse the northwestern quadrant of the CONUS over the next few
hours. Pockets of cooler temperatures aloft with these impulses may
support just enough buoyancy (however scant) for a few lightning
flashes across portions of northwestern Wyoming and the Pacific
Northwest coastline through early tonight.

..Squitieri.. 12/20/2025

$$

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ACUS01 KWNS 200521
SWODY1
SPC AC 200520

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1120 PM CST Fri Dec 19 2025

Valid 201200Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated lightning flashes may occur near coastal sections of
Washington today.

...Synopsis...
A mid-level trough will progress across the eastern CONUS while
upper ridging builds west of the Rockies, resulting in surface high
pressure overspreading the Midwest as a surface trough impinges on
the Pacific Northwest Coastline. Cooler temperatures aloft will
overspread a marine boundary layer over the Washington coast,
resulting in scant buoyancy, which may favor a few convective
updrafts that may deepen enough to produce isolated lightning
flashes. A weakening surface low will also drift southward across
the southern Plains, promoting low-level moisture return inland from
the western Gulf. However, considerable convective inhibition should
limit convective development through the Day 1 period.

..Squitieri.. 12/20/2025

$$

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ACUS01 KWNS 201234
SWODY1
SPC AC 201232

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0632 AM CST Sat Dec 20 2025

Valid 201300Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected, but a few lightning flashes
may occur today near coastal Washington.

...Discussion...
Progressive/low-amplitude flow aloft will prevail over the CONUS to
the south of an amplifying shortwave trough over the Great
Lakes/Ontario. Surface high pressure will expand eastward across the
Plains and Midwest. Some inland moistening will occur across east
Texas toward the Lower Mississippi Valley via the western Gulf, but
weak forcing/capping will hinder appreciable convective development.
In the Pacific Northwest, a marginally supportive thermodynamic
environment may allow for a few lightning flashes near the
Washington coast today and tonight.

..Guyer/Marsh.. 12/20/2025

$$

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ACUS01 KWNS 201554
SWODY1
SPC AC 201553

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0953 AM CST Sat Dec 20 2025

Valid 201630Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few lightning flashes may occur today near coastal Washington, and
tonight over southern Louisiana.

Dry and stable conditions will prevail over most of the CONUS today,
precluding thunderstorms. One exception will be over western WA
west of the Cascades, where fast onshore flow, orographic lift, and
100-200 J/kg of CAPE will be present. The other area of some risk
of lightning will be over southern LA tonight in a weak low-level
warm advection regime. In both areas, thunderstorm coverage is
anticipated to be sparse and severe risk negligible.

..Hart/Karstens.. 12/20/2025

$$

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ACUS01 KWNS 201937
SWODY1
SPC AC 201935

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0135 PM CST Sat Dec 20 2025

Valid 202000Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few lightning flashes may occur today across parts of coastal Washington/Oregon and tonight over southern Louisiana. Severe
thunderstorms are not expected.

...20Z Update...
No changes have been made to the ongoing forecast. See the previous
discussion below for more information.

..Gleason.. 12/20/2025

.PREV DISCUSSION... /ISSUED 0953 AM CST Sat Dec 20 2025/

Dry and stable conditions will prevail over most of the CONUS today,
precluding thunderstorms. One exception will be over western WA
west of the Cascades, where fast onshore flow, orographic lift, and
100-200 J/kg of CAPE will be present. The other area of some risk
of lightning will be over southern LA tonight in a weak low-level
warm advection regime. In both areas, thunderstorm coverage is
anticipated to be sparse and severe risk negligible.

$$

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ACUS01 KWNS 210034
SWODY1
SPC AC 210033

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0633 PM CST Sat Dec 20 2025

Valid 210100Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few lightning flashes may occur late tonight over southern
Louisiana; however, this activity will be very sparse.

...01z Update...

Weak surface front is expected to settle into northern LA, arcing
southwest into the Hill Country of central TX by the end of the
period. Favorable low-level trajectories will continue across the
western Gulf basin into southern LA tonight where 60s surface dew
points are expected to hold. However, large-scale forcing is not
expected to be particularly notable and a fairly strong cap is
currently noted around 2km on the 00z LCH sounding. Latest model
guidance suggests this capping will likely persist, but possibly
weaken toward 12z. If so, a few flashes of lightning may accompany
weak convection across southern LA.

..Darrow.. 12/21/2025

$$

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ACUS01 KWNS 210516
SWODY1
SPC AC 210514

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1114 PM CST Sat Dec 20 2025

Valid 211200Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today.

...Pacific Northwest...

Low-amplitude short-wave trough is forecast to approach the Pacific
Northwest coast later this evening as modest midlevel height falls
spread inland across WA/OR. Latest model guidance suggests weak
buoyancy will persist much of the period, particularly near the
coast, where onshore flow will contribute to SBCAPE generally less
than 100 J/kg. As freezing levels lower, shallow convection may
penetrate levels necessary for lightning discharge. For these
reasons will maintain 10% probability for isolated thunderstorms,
primarily near the coast.

..Darrow/Squitieri.. 12/21/2025

$$

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ACUS01 KWNS 211254
SWODY1
SPC AC 211253

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0653 AM CST Sun Dec 21 2025

Valid 211300Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today.

...Discussion...
A progressive/zonal upper-flow pattern will continue over the CONUS.
A low-amplitude shortwave trough will move inland across the Pacific
Northwest by tonight. Weak buoyancy and cooling temperatures aloft
may become sufficient for isolated lightning flashes, particularly
near the Washington coast. Farther south, a moisture-rich plume and
a marginally favorable thermodynamic environment may allow for some
lighting flashes across northern California.

Elsewhere, a relatively moist airmass near/south of a
southward-moving front, along with continued weak warm/moist
advection, will probably be conducive for isolated thunderstorms
mainly across southern portions of Louisiana and Mississippi today.

..Guyer/Marsh.. 12/21/2025

$$

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ACUS01 KWNS 211558
SWODY1
SPC AC 211557

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0957 AM CST Sun Dec 21 2025

Valid 211630Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today.

Thunderstorm potential will be limited across the CONUS. Strong
onshore flow and cold temperatures aloft will pose a risk of a few
lightning flashes today and tonight over portions of the WA/OR coast
and parts of northern CA. Low-level warm advection and an
approaching cold front could result in isolated thunderstorms this
afternoon over parts of southern LA/MS, and late tonight over south
TX. No severe storms are anticipated today.

..Hart/Karstens.. 12/21/2025

$$

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ACUS01 KWNS 211925
SWODY1
SPC AC 211923

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0123 PM CST Sun Dec 21 2025

Valid 212000Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today.

...20z Update...
No changes are needed to the D1 Convective Outlook. See previous
discussion below.

..Thornton.. 12/21/2025

.PREV DISCUSSION... /ISSUED 0957 AM CST Sun Dec 21 2025/

Thunderstorm potential will be limited across the CONUS. Strong
onshore flow and cold temperatures aloft will pose a risk of a few
lightning flashes today and tonight over portions of the WA/OR coast
and parts of northern CA. Low-level warm advection and an
approaching cold front could result in isolated thunderstorms this
afternoon over parts of southern LA/MS, and late tonight over south
TX. No severe storms are anticipated today.

$$

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ACUS01 KWNS 220051
SWODY1
SPC AC 220049

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0649 PM CST Sun Dec 21 2025

Valid 220100Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected tonight.

...01z Update...

Potential for lighting is negligible across most of the CONUS
tonight. A few exceptions are along the LA and south TX coasts, and
across portions of the Pacific Northwest. Isolated thunderstorms
have recently developed along a frontal zone across southern LA.
This activity will gradually propagate off the LA coast later this
evening and focus offshore. Some risk for weak convection also
extends across south TX along this frontal zone.

A notable short-wave trough is advancing toward the WA/OR coast
early this evening. A few flashes of lightning have been observed
off Vancouver Island with this feature. Some risk for isolated
thunderstorms continues near the coast as the surface front surges
inland and profiles cool.

..Darrow.. 12/22/2025

$$

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ACUS01 KWNS 220523
SWODY1
SPC AC 220521

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1121 PM CST Sun Dec 21 2025

Valid 221200Z - 231200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast today.

...Discussion...

Midlevel short-wave trough, off the Pacific Northwest coast, is
forecast to advance inland around 23/00z before deamplifying as it
ejects into southwest Canada by the end of the period. Associated
surface front will also progress inland around 23/00z, and cooling
lower tropospheric profiles should lead to weak buoyancy along the
WA/OR coast. Low-topped convection may generate a flash or two of
lightning, but thunderstorms should otherwise remain quite sparse.

Late-evening water-vapor imagery depicts a weak short-wave trough
over northeast Mexico, lifting north in line with latest model
guidance. Deep southeasterly flow across south TX will maintain
moist profiles that should exhibit modest SBCAPE by late afternoon.
Forecast soundings also suggest deep-layer shear will remain quite
weak, and any convection that evolves across this region should
remain below severe levels.

..Darrow/Squitieri.. 12/22/2025

$$

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ACUS01 KWNS 221252
SWODY1
SPC AC 221250

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0650 AM CST Mon Dec 22 2025

Valid 221300Z - 231200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today.

...Discussion...
The next shortwave trough and associated cold front are expected to
advance inland across British Columbia/coastal Washington by this
evening. A related plume of steepening mid-level lapse rates will
contribute to weak buoyancy and the potential for isolated lightning
flashes with low-topped convection. Elsewhere across the West, a few
lightning flashes have been noted early this morning across the
California Sierra, and this scenario may continue today within a
moisture-rich plume with weak buoyancy.

A weak mid-level disturbance over the western Gulf and coastal
Mexico, along with a moist air mass (reference 12z Brownsville
observed sounding) to the south of a slow-moving front, may allow
for a few thunderstorms to develop into/across Deep South Texas.
Similar to morning RAOB/WSR-88D VWP observations, forecast soundings
suggest deep-layer shear will remain quite weak, such that any
convection that evolves across this region should remain below
severe levels.

..Guyer/Marsh.. 12/22/2025

$$

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ACUS01 KWNS 221610
SWODY1
SPC AC 221608

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1008 AM CST Mon Dec 22 2025

Valid 221630Z - 231200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today.

...Synopsis...
A pronounced midlevel shortwave trough and associated baroclinic
zone will move across the WA coast later this afternoon.
Low-midlevel lapse rates will contribute to weak buoyancy of
sufficient depth (through -20 C at the equilibrium level) for charge
separation and isolated lightning flashes with low-topped convection
along and behind the front. Shallow, weakly rotating convection
will be possible near the WA coast per the KLGX VWP/hodograph, but
the threat for severe storms appears too limited to warrant an
outlook area. Farther south, the potential for isolated lightning
flashes will slowly wane through the day across the northern Sierra
Nevada, where weak buoyancy rooted above the surface will likewise
diminish.

Otherwise, a broad subtropical ridge (with unusually high
geopotential heights) covers the southern Plains/Gulf coast. An
embedded/weak midlevel trough will rotate slowly north-northwestward
around the periphery of the ridge, bringing weak ascent and an
associated moisture plume into south TX. Per the observed deepening
of the moist layer at BRO in the past 12 hours, pockets of surface heating/destabilization could support isolated thunderstorm
development across south TX this afternoon.

..Thompson/Thornton.. 12/22/2025

$$

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ACUS01 KWNS 221937
SWODY1
SPC AC 221936

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0136 PM CST Mon Dec 22 2025

Valid 222000Z - 231200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today.

...20z Update...
The previous outlook reasoning remains on track and no changes were
made with this update.

..Bunting.. 12/22/2025

.PREV DISCUSSION... /ISSUED 1008 AM CST Mon Dec 22 2025/

...Synopsis...
A pronounced midlevel shortwave trough and associated baroclinic
zone will move across the WA coast later this afternoon.
Low-midlevel lapse rates will contribute to weak buoyancy of
sufficient depth (through -20 C at the equilibrium level) for charge
separation and isolated lightning flashes with low-topped convection
along and behind the front. Shallow, weakly rotating convection
will be possible near the WA coast per the KLGX VWP/hodograph, but
the threat for severe storms appears too limited to warrant an
outlook area. Farther south, the potential for isolated lightning
flashes will slowly wane through the day across the northern Sierra
Nevada, where weak buoyancy rooted above the surface will likewise
diminish.

Otherwise, a broad subtropical ridge (with unusually high
geopotential heights) covers the southern Plains/Gulf coast. An
embedded/weak midlevel trough will rotate slowly north-northwestward
around the periphery of the ridge, bringing weak ascent and an
associated moisture plume into south TX. Per the observed deepening
of the moist layer at BRO in the past 12 hours, pockets of surface heating/destabilization could support isolated thunderstorm
development across south TX this afternoon.

$$

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ACUS01 KWNS 230029
SWODY1
SPC AC 230027

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0627 PM CST Mon Dec 22 2025

Valid 230100Z - 231200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorm probabilities are low tonight.

...01z Update...

Water-vapor imagery depicts a notable short-wave trough advancing
inland along the Pacific Northwest coast. A few flashes of lighting
have been observed with deeper convection ahead of this feature,
primarily across more buoyant regions offshore. While an isolated
thunderstorm can not be ruled out for the next few hours, lightning probabilities appear too low to warrant a categorical risk of
thunderstorms the rest of tonight.

Lighting has decreased notably across the western Gulf basin in
association with a weak disturbance lifting north toward deep South
TX. 00z sounding at BRO does exhibit uninhibited SBCAPE, but loss of
daytime heating and weak forcing does not appear particularly
favorable for more than a rogue flash of lightning, and that is
primarily over the next few hours.

..Darrow.. 12/23/2025

$$

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ACUS01 KWNS 230521
SWODY1
SPC AC 230519

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1119 PM CST Mon Dec 22 2025

Valid 231200Z - 241200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorm potential will increase along the California coast late
tonight. Organized severe is not currently forecast.

...CA...

Strong short-wave trough is forecast to approach the northern CA
coast after 24/06z, then eject inland by sunrise as midlevel speed
max intensifies and translates into northern CA. Latest model
guidance suggests this feature will induce a surface low that should
deepen as it approaches the northern CA/OR coast. This evolution
will allow a notable surface front to surge inland toward the end of
the period, around 24/12z. Wind profiles are expected to increase
markedly ahead of this feature, but pre frontal buoyancy will remain
quite limited. Forecast soundings support this with roughly 100-200
J/kg MUCAPE expected just ahead of the front. Given the strength of
the wind field there is some concern that a few strong gusts could
be noted with deeper convection; however, this activity should
develop very late (after 09z), possibly becoming more problematic
during the day2 period. At this time will not introduce severe
probabilities due to the expected late-period development, but will
continue to monitor for possible upgrade.

...South TX...

Weak midlevel disturbance is lifting north into deep south TX late
this evening. Forecast soundings suggest modest SBCAPE will develop
by mid day as this feature progresses north of the international
border. Wind fields should remain weak, along with forcing, so the
risk of severe is expected to remain low this period.

..Darrow/Squitieri.. 12/23/2025

$$

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ACUS01 KWNS 231300
SWODY1
SPC AC 231259

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0659 AM CST Tue Dec 23 2025

Valid 231300Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS NEAR THE COAST
OF NORTHERN CALIFORNIA...

...SUMMARY...
A localized threat for severe gusts may develop late tonight near
the coast in northern California.

...CA...
A potent shortwave trough is forecast to approach the northern CA
coast late tonight as an attendant midlevel speed max moves from the
eastern Pacific into northern CA. Considerable differences were
noted in some of the latest models with the 00z EC/UKMET operational
runs considerably weaker with cyclone development than 00-06z runs
of the NAM/GFS/Canadian and the 00z HREF mean. Hedging towards a
slightly more intense forecast solution and related wind field
depictions. This forecast scenario coincides with a surface front
surging inland toward the end of the period, around 24/12z. Although pre-frontal buoyancy will remain quite limited (100-200
J/kg MUCAPE), the deeper low-topped convection may yield a
severe-wind risk during the 08-12z period near the immediate coast
before buoyancy diminishes inland.

...South TX...
Weak midlevel disturbance is lifting north into deep south TX late
this evening. Forecast soundings suggest modest SBCAPE will develop
by mid day as this feature progresses north of the international
border. Wind fields should remain weak, along with forcing, so the
risk of severe is expected to remain low this period.

..Smith/Weinman.. 12/23/2025

$$

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ACUS01 KWNS 231621
SWODY1
SPC AC 231620

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1020 AM CST Tue Dec 23 2025

Valid 231630Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
COASTAL CALIFORNIA...

...SUMMARY...
An isolated threat for severe/damaging gusts and perhaps a brief
tornado may develop late tonight/early Wednesday morning across
parts of coastal California.

...California...
Within large-scale upper troughing over the eastern Pacific, an
embedded mid-level shortwave trough will move quickly eastward and
approach the CA Coast late tonight/early Wednesday morning. A
corresponding strengthening and increase in the flow through much of
the troposphere is anticipated late in the period, with a surface
low also forecast to deepen along/near the coast of northern CA. A
cold front attendant to this surface low will sweep quickly
eastward, and should be approaching/onshore across parts of coastal northern/central CA by 12Z early Wednesday morning. Current
expectations are for the thermodynamic profile to remain mostly
saturated, with poor lapse rates generally limiting instability.
Even so, it appears that a gradual increase in low-level moisture
ahead of the cold front and slightly cooling mid-level temperatures
with the approach of the shortwave trough may support weak but
sufficient MUCAPE for an organized band of low-topped thunderstorms
late tonight.

Most guidance suggests this convection will not impact parts of
coastal CA until after 24/06Z, and there is still significant
uncertainty whether enough boundary-layer instability will be
present to support surface-based convection. There is also a signal
for pre-frontal convection in the low-level warm advection regime
across parts of central into coastal southern CA. Given the strength
of the low/mid-level flow forecast, and related strong
low-level/deep-layer shear, it appears that convectively enhanced
winds may be capable of reaching severe levels and producing damage
on an isolated basis even if instability remains minimal. A brief
tornado may also occur if convection can become truly surface based,
as effective SRH will be enhanced by a 50-70 kt southerly low-level
jet. Based on latest guidance trends, the Marginal Risk has been
expanded southward along the coast to include more of
central/southern CA. This isolated severe threat is expected to
continue beyond 12Z Wednesday into the Day 2 period.

..Gleason/Thornton.. 12/23/2025

$$

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ACUS01 KWNS 231947
SWODY1
SPC AC 231945

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0145 PM CST Tue Dec 23 2025

Valid 232000Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
COASTAL CALIFORNIA...

...SUMMARY...
An isolated threat for severe/damaging gusts and perhaps a brief
tornado may develop late tonight/early Wednesday morning across
parts of coastal California.

...20Z Update...
Relatively minor adjustments to the general thunder forecast were
made based on the latest observations and model guidance. The
remainder of the forecast remains unchanged. See the previous
discussion for additional information.

..Wendt.. 12/23/2025

.PREV DISCUSSION... /ISSUED 1020 AM CST Tue Dec 23 2025/

...California...
Within large-scale upper troughing over the eastern Pacific, an
embedded mid-level shortwave trough will move quickly eastward and
approach the CA Coast late tonight/early Wednesday morning. A
corresponding strengthening and increase in the flow through much of
the troposphere is anticipated late in the period, with a surface
low also forecast to deepen along/near the coast of northern CA. A
cold front attendant to this surface low will sweep quickly
eastward, and should be approaching/onshore across parts of coastal northern/central CA by 12Z early Wednesday morning. Current
expectations are for the thermodynamic profile to remain mostly
saturated, with poor lapse rates generally limiting instability.
Even so, it appears that a gradual increase in low-level moisture
ahead of the cold front and slightly cooling mid-level temperatures
with the approach of the shortwave trough may support weak but
sufficient MUCAPE for an organized band of low-topped thunderstorms
late tonight.

Most guidance suggests this convection will not impact parts of
coastal CA until after 24/06Z, and there is still significant
uncertainty whether enough boundary-layer instability will be
present to support surface-based convection. There is also a signal
for pre-frontal convection in the low-level warm advection regime
across parts of central into coastal southern CA. Given the strength
of the low/mid-level flow forecast, and related strong
low-level/deep-layer shear, it appears that convectively enhanced
winds may be capable of reaching severe levels and producing damage
on an isolated basis even if instability remains minimal. A brief
tornado may also occur if convection can become truly surface based,
as effective SRH will be enhanced by a 50-70 kt southerly low-level
jet. Based on latest guidance trends, the Marginal Risk has been
expanded southward along the coast to include more of
central/southern CA. This isolated severe threat is expected to
continue beyond 12Z Wednesday into the Day 2 period.

$$

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ACUS01 KWNS 240054
SWODY1
SPC AC 240053

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0653 PM CST Tue Dec 23 2025

Valid 240100Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
COASTAL CALIFORNIA...

...SUMMARY...
An isolated threat for severe/damaging gusts and perhaps brief
tornadoes may develop late tonight/early Wednesday morning across
parts of coastal California.

... 01Z Update ...

A strong short-wave trough/surface low continues to approach the California/Oregon coast. Later tonight a midlevel speed max will
intensify, helping to deepen the surface low, which will drive a
cold front eastward into California during the overnight and morning
hours. Despite limited buoyancy, especially surface based,
strengthening tropospheric flow and forced convection along the cold
front may support isolated damaging wind gusts along the California
coast. Should truly surface-based buoyancy develop and the forced
convection can realize this buoyancy, forecast wind profiles along
the coast exhibit sufficient deep-layer shear and low-level
curvature to support brief tornadoes. The easternmost extent of this
threat, especially across southern California, is delineated by the
expected position of the surface-cold front at 12Z/4AM PT. The
threat will continue past 12Z/4AM PT.

..Marsh.. 12/24/2025

$$

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ACUS01 KWNS 240554
SWODY1
SPC AC 240553

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1153 PM CST Tue Dec 23 2025

Valid 241200Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS COASTAL
CALIFORNIA AND THE CENTRAL VALLEY...

...SUMMARY...
Thunderstorms with marginally severe wind gusts, small hail and
potentially a brief tornado will be possible from Wednesday into
Wednesday night along parts of the California coast, and inland
across the San Joaquin Valley.

... Synopsis ...

A high-amplitude midlevel pattern will persist on Wednesday,
characterized by a deep trough across the eastern Pacific and a
building ridge across the Plains. This pattern will maintain a broad
belt of intense cyclonic flow across California into the Interior
West.

Throughout the day, an initial shortwave trough will continue
lifting northeast from the eastern Pacific into the Pacific
Northwest, while the attendant surface low lifts more northward
along the coast toward Washington. Late on Wednesday a second, more
potent trough will approach central and northern California --
primarily after dark. This setup will facilitate a prolonged period
rain and embedded thunderstorms across California and portions of
the Interior West into Thursday.

... California Coast ...

Strong ascent and strengthening onshore flow will aid in modest
destabilization Wednesday morning ahead of a surface cold front. An
ongoing band of convection is expected across the central and
southern coastal areas associated with the strongly forced ascent
along the advancing cold front. Given the presence of a strong
low-level jet (locally exceeding 50 knots at 1 km AGL), there is a
risk that these strong winds will mix to the surface within the
strongest convection resulting in damaging wind gusts. Forecast
soundings across the area do maintain some low-level curvature ahead
of the convective line, such that any convective element able to
interact with true surface-based buoyancy would have the potential
for a brief tornado.

In the wake of the morning convection, a secondary surface low will
intensify during the afternoon and overnight as it approaches the
northern California coast. This will likely trigger another round or
two of broken, low-topped convection along a second cold front.
Despite weaker instability than with the morning convection, the
strength of the wind fields would suggest an ongoing risk for
isolated wind damage as this convection moves inland.

... Central Valley ...

Cold midlevel temperatures and increasing height falls will
overspread surface dewpoints in the 40s to perhaps low 50s. Although
buoyancy will remain modest (MUCAPE at or below 500 J/kg), the
presence of a powerful midlevel jet in excess of 100 knots will
support long hodographs. This combination of modest instability and
large/long hodographs may support a threat for semi-organized
convection, including some potential for supercells. The strongest
storms will be capable of producing damaging gusts, hail, and a
brief tornado before the convection shifts east into the higher
terrain and weakens.

..Marsh/Squitieri.. 12/24/2025

$$

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ACUS01 KWNS 241256
SWODY1
SPC AC 241255

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0655 AM CST Wed Dec 24 2025

Valid 241300Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS COASTAL
CALIFORNIA AND THE CENTRAL VALLEY...

...SUMMARY...
An isolated risk for localized severe gusts and perhaps a brief
tornado will exist today into tonight along much of the California
coast and the central valley.

...California...
Water-vapor early this morning shows an upper trough over the
eastern Pacific with a lead disturbance moving north near the
northern coast of CA/southwest OR. Farther south, a mid-level
vorticity maximum west of southern CA will move to the Sierra Nevada
by early evening. Upstream of this disturbance and farther west,
models show a more potent mid-level shortwave trough moving
northeast towards the northern CA coast by 25/12z. In the low
levels, a notable deepening of a cyclone is forecast tonight over
the eastern Pacific to the west of the northern coast of CA.

Zone of persistent and strong low-level WAA regime will aid in
maintaining a persistent rain shield with shallow convection from
Point Conception southward along the coast into the LA Basin this
morning. Scant buoyancy will limit updraft vigor/depth, but intense
flow (reference KVBX, KVTX WSR-88D VAD data) in the lowest 2-km MSL
may enable an isolated risk for wind damage/severe gusts near the
coast and in terrain-favored locales. A brief tornado cannot be
ruled out, but this threat would likely depend on the development of
stronger embedded convective elements within the larger rain shield.

Later this afternoon, some convection-allowing models show
low-topped convection developing within the central valley in an
environment characterized by cold mid-level temperatures and a
modestly moist airmass. A mini supercell risk is possible with an
attendant isolated threat for a brief tornado and wind.

By early evening, another round of low-topped convection is progged
to develop west of the coast. This activity will focus from near
Point Conception northward along the coast tonight as strengthening
ascent accompanies the approach of the next mid-level wave.
Elongated hodographs and weak buoyancy will support potential storm organization with the stronger storms and an isolated threat for
severe wind gusts/brief tornado.

..Smith/Weinman.. 12/24/2025

$$

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ACUS01 KWNS 241627
SWODY1
SPC AC 241625

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1025 AM CST Wed Dec 24 2025

Valid 241630Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
COASTAL CALIFORNIA AND PORTIONS OF THE CENTRAL VALLEY...

...SUMMARY...
An isolated risk for severe/damaging gusts and perhaps a brief
tornado will exist today into tonight along much of the California
Coast and portions of the Central Valley.

...California...
A shallow band of pre-frontal convection may continue to pose a
threat for locally severe/damaging winds (especially across higher terrain/ridgetops) and perhaps a brief tornado this morning across
parts of coastal southern CA. This activity is being supported by
strong low-level warm advection and large-scale ascent associated
with an enhanced mid/upper-level jet. Current expectations are for
this activity to continue moving eastward through the afternoon
across the remainder of coastal southern CA in a strongly sheared
environment. However, various NAM/RAP forecast soundings across this
area suggest that even with low 60s surface dewpoints and
modest/filtered daytime heating, the overall severe threat will
likely remain isolated due to poor lapse rates aloft and limited
boundary-layer instability. Reference Mesoscale Discussion 2269 for
more details on the near-term severe threat across southern CA.

Additional rounds of convection are expected later this evening and
overnight into early Thursday morning over portions of
northern/central CA, as multiple mid-level shortwave troughs
embedded within persistent large-scale upper troughing over the
eastern Pacific overspread these areas. One such shortwave trough is
forecast to advance over coastal central CA and vicinity around
25/00-06Z this evening, with cool temperatures aloft (less than -20C
at 500 mb) supporting weak MUCAPE. Both low-level and deep-layer
shear are expected to gradually increase this evening as the
shortwave trough approaches, with some updraft organization
possible. Strong to locally severe winds and a brief tornado or two
appear possible with this activity, but uncertainty is still
substantial whether sufficient instability will be present to
support surface-based thunderstorms.

A stronger mid-level shortwave trough will move east-northeastward
from the eastern Pacific and approach the northern CA Coast by 12Z
Thursday morning, along with a deepening surface low and attendant
cold front. A 70-80+ kt mid-level jet will accompany this shortwave
trough, along with a 50-60 kt south-southwesterly low-level jet. A
broken band of low-topped thunderstorms will likely develop in
association with this shortwave trough along/ahead of the front, and
overspread coastal portions of northern/central CA late tonight
through early Thursday morning (25/06-12Z). A strongly sheared
environment and weak but sufficient MLCAPE may exist to support at
least an isolated threat for severe/damaging winds and a tornado or
two as this activity spreads inland through the end of the period.
Still, the overall severe threat should be tempered by the lack of
stronger instability.

Finally, some chance for low-topped/mini supercells may exist late
this afternoon/evening across parts of the Central Valley of CA. If
these thunderstorms can develop and be sustained, they could pose a
threat for both damaging winds and a brief tornado. But, confidence
in this scenario occurring remains rather low.

..Gleason/Bunting.. 12/24/2025

$$

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ACUS01 KWNS 241952
SWODY1
SPC AC 241950

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0150 PM CST Wed Dec 24 2025

Valid 242000Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
COASTAL CALIFORNIA AND PORTIONS OF THE CENTRAL VALLEY...

...SUMMARY...
An isolated risk for severe/damaging gusts and perhaps a brief
tornado will exist today into tonight along much of the California
Coast and portions of the Central Valley.

...20Z Update...

...Central/Northern California...
Water vapor imagery shows the shortwave trough already moving
inland. In the wake of this activity, visible satellite shows
potential for cloud cover to reduce within the Central Valley from
west to east. Some forecast soundings show destabilization is
possible by late afternoon. Given the southeast flow within the
Valley and strong flow aloft, a conditional threat for a marginal supercell/brief tornado could develop.

Greater confidence exists with activity later in the evening into
Thursday morning associated with a secondary, stronger shortwave
trough. Another narrow band of convection is expected ahead of this
shortwave and will impact parts of the central/northern California
Coast and eventually parts of the Central Valley as well. Isolated
damaging winds and a brief tornado would be possible with this
activity.

...Southern California...
A spatially limited threat for wind damage and a brief tornado will
exist for another few hours this afternoon. A low-topped band of
convection recently moved through much of the LA Basin and will
generally continue eastward. There may be a narrow sliver of
dewpoints near 60 F just east of this activity. Dewpoints closer to
San Diego are only in the upper 50s F, however. Strong wind shear at
low levels will maintain this marginal risk, though decreasing
buoyancy southward and inland should lead to a downward trend in
intensity.

..Wendt.. 12/24/2025

.PREV DISCUSSION... /ISSUED 1025 AM CST Wed Dec 24 2025/

...California...
A shallow band of pre-frontal convection may continue to pose a
threat for locally severe/damaging winds (especially across higher terrain/ridgetops) and perhaps a brief tornado this morning across
parts of coastal southern CA. This activity is being supported by
strong low-level warm advection and large-scale ascent associated
with an enhanced mid/upper-level jet. Current expectations are for
this activity to continue moving eastward through the afternoon
across the remainder of coastal southern CA in a strongly sheared
environment. However, various NAM/RAP forecast soundings across this
area suggest that even with low 60s surface dewpoints and
modest/filtered daytime heating, the overall severe threat will
likely remain isolated due to poor lapse rates aloft and limited
boundary-layer instability. Reference Mesoscale Discussion 2269 for
more details on the near-term severe threat across southern CA.

Additional rounds of convection are expected later this evening and
overnight into early Thursday morning over portions of
northern/central CA, as multiple mid-level shortwave troughs
embedded within persistent large-scale upper troughing over the
eastern Pacific overspread these areas. One such shortwave trough is
forecast to advance over coastal central CA and vicinity around
25/00-06Z this evening, with cool temperatures aloft (less than -20C
at 500 mb) supporting weak MUCAPE. Both low-level and deep-layer
shear are expected to gradually increase this evening as the
shortwave trough approaches, with some updraft organization
possible. Strong to locally severe winds and a brief tornado or two
appear possible with this activity, but uncertainty is still
substantial whether sufficient instability will be present to
support surface-based thunderstorms.

A stronger mid-level shortwave trough will move east-northeastward
from the eastern Pacific and approach the northern CA Coast by 12Z
Thursday morning, along with a deepening surface low and attendant
cold front. A 70-80+ kt mid-level jet will accompany this shortwave
trough, along with a 50-60 kt south-southwesterly low-level jet. A
broken band of low-topped thunderstorms will likely develop in
association with this shortwave trough along/ahead of the front, and
overspread coastal portions of northern/central CA late tonight
through early Thursday morning (25/06-12Z). A strongly sheared
environment and weak but sufficient MLCAPE may exist to support at
least an isolated threat for severe/damaging winds and a tornado or
two as this activity spreads inland through the end of the period.
Still, the overall severe threat should be tempered by the lack of
stronger instability.

Finally, some chance for low-topped/mini supercells may exist late
this afternoon/evening across parts of the Central Valley of CA. If
these thunderstorms can develop and be sustained, they could pose a
threat for both damaging winds and a brief tornado. But, confidence
in this scenario occurring remains rather low.

$$

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ACUS01 KWNS 250055
SWODY1
SPC AC 250054

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0654 PM CST Wed Dec 24 2025

Valid 250100Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ALONG MUCH OF
THE CALIFORNIA COAST AND PORTIONS OF THE CENTRAL VALLEY...

...SUMMARY...
An isolated risk for severe/damaging gusts and perhaps a brief
tornado will exist through tonight along much of the California
Coast and portions of the Central Valley.

... 01Z Update ...

Multiple bands of convection look likely this evening into the early
morning hours as a deepening surface low approaches the California
coast. The strongest convective elements within this first band,
currently approaching the San Francisco Bay area, will be capable of
producing gusty winds as it moves inland.

Wind fields will strengthen overnight in response to the approaching
low. This will maintain sufficient low-level theta-e advection to
support modest low-level instability through Christmas morning.
Numerical guidance this evening indicates a more intense band of
convection will approach the central and northern California coast
in the 08-12Z (12-4AM PT) window, quickly moving into northern
portions of the Central Valley. Given the modest instability and
strong wind fields, isolated strong wind gusts and a brief tornado
will be possible overnight, especially along the coast.

Elsewhere along the California coast, low-level moist advection will
persist through the night supporting localized convective
development. For the same reasons listed above, an isolated strong
wind gust or brief tornado would be possible with these convective
elements.

... Central Valley ...

Thunderstorms have developed this afternoon across portions of the
Central Valley near Sacramento. Surface-based instability around 500
J/kg within a strongly sheared environment will support an isolated
wind threat. Should convective elements become more cellular, the
low-level wind fields would support a brief tornado, especially in
areas where surface-based instability can be realized. This activity
will lift generally northward across the Central Valley through this
evening.

..Marsh.. 12/25/2025

$$

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ACUS01 KWNS 250538
SWODY1
SPC AC 250537

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1137 PM CST Wed Dec 24 2025

Valid 251200Z - 261200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR MUCH OF THE
CALIFORNIA COAST AND PORTIONS OF THE CENTRAL VALLEY...

...SUMMARY...
Thunderstorms with potential to produce marginally severe wind gusts
and perhaps a brief tornado will be possible on Thursday along much
of the California Coast and portions of the Central Valley.

... Synopsis ...

A highly amplified pattern will persist across the US as a deep
trough over the eastern Pacific is maintained and a ridge builds
over the central US. A series of embedded shortwave troughs within
the eastern Pacific trough will impact the West Coast on Christmas
and Christmas night.

... California ...

The first of these shortwave troughs will be moving across the
region at the start of the forecast period, bringing with it a band
of strongly forced convection, likely located across portions of the
central coast of California into the Central Valley. As the
shortwave trough takes on an increasingly negative tilt, a 50-60
knot southerly low-level jet will be maintained allowing for
sufficient low-level theta-e advection to support a modest 100-300
J/kg of surface-based CAPE. As the convective band interacts with
this strong low-level kinematic field, gusty/damaging convective
winds may be realized at the surface, particularly with the stronger
convective elements. Forecast low-level hodographs ahead of this
convective line feature sufficient low-level curvature to support a
brief tornado should any convective element realize true
surface-based buoyancy. As the morning progresses, the
aforementioned shortwave trough will lift north then northwest
within the broader cyclonic flow across the eastern Pacific whereas
the band of convection slowly advances south and east. By midday,
the low-level wind fields should weaken sufficiently in response to
the departing shortwave trough to reduce the potential of damaging winds/tornadoes across far southern California.

By mid-afternoon, another shortwave trough will approach the central
and northern California coast. In response, the low-level wind
fields will once again strengthen, albeit perhaps not to the extent
as with the morning wave. Another band or bands of strongly forced
convection are expected to develop across the eastern Pacific and
approach coastal areas of central California after 00Z (4 PM PT). As
was the case with the morning convection, the strongest convective
elements may be capable of mixing down the stronger winds aloft
resulting in the potential for isolated strong thunderstorm winds.

..Marsh/Squitieri.. 12/25/2025

$$

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ACUS01 KWNS 251245
SWODY1
SPC AC 251244

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0644 AM CST Thu Dec 25 2025

Valid 251300Z - 261200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR MUCH OF THE
CALIFORNIA COAST AND PORTIONS OF THE CENTRAL VALLEY...

...SUMMARY...
An isolated risk for severe gusts and localized wind damage, and
perhaps a brief tornado will be possible today along much of the
California Coast and portions of the Central Valley.

... California ...
Water-vapor imagery early this morning shows a mid-level low over
the eastern Pacific and a negative-tilt shortwave trough moving
northward along the northern CA and OR coast. An upstream mid-level
speed max and associated vorticity max will move cyclonically
through the base of the eastern Pacific low/trough and approach San
Francisco Bay and northern CA this evening and subsequently move
into eastern OR by early Friday morning.

Strong to locally severe thunderstorms mainly capable of a
severe-wind hazard will potentially continue on an isolated basis
this morning from the Central Valley/central coast and perhaps
include portions of southern CA. The low CAPE/high shear
environment will potentially support strong/locally severe
convection contingent on sufficient updraft development. Forecast
low-level hodographs will remain sufficiently enlarged to yield a
low risk for a brief tornado across much of the Marginal Risk (level
1 of 5) area. By this afternoon, model guidance indicates low-level
flow will weaken before re-intensifying towards evening in
association with the arrival of the next speed max. A mix of linear
bands and cellular convective structures may continue to pose an
intermittent risk for isolated damaging gusts and perhaps a brief
tornado into tonight.

..Smith/Weinman.. 12/25/2025

$$

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ACUS01 KWNS 251627
SWODY1
SPC AC 251626

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1026 AM CST Thu Dec 25 2025

Valid 251630Z - 261200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
COASTAL CALIFORNIA AND PORTIONS OF THE CENTRAL VALLEY...

...SUMMARY...
An isolated risk for severe gusts/localized wind damage and perhaps
a brief tornado will be possible today into this evening along much
of the California Coast and portions of the Central Valley.

...California...
Recent satellite imagery shows a mid/upper-level low over the
eastern Pacific and a negative-tilt shortwave trough moving
northward along the northern CA and OR Coast. An upstream mid-level
jet and associated vorticity maximum will move through the base of
the eastern Pacific upper low/trough and approach the San Francisco
Bay and northern CA vicinity this evening.

Strong to locally severe thunderstorms capable of producing mainly
isolated severe/damaging winds will remain possible with convection
today into this evening. Weak instability is forecast to persist
across much of coastal CA into the Central Valley, with cool surface temperatures, saturated profiles, and modest lapse rates aloft
(reference the 12Z OAK sounding) limiting the development of greater
MUCAPE. Still, a favorable kinematic environment with enhanced west-southwesterly mid/upper-level flow will conditionally support
occasional strong to severe convection, contingent on sufficiently deep/sustained updraft development.

Low-level hodographs are forecast to remain enlarged enough to yield
a low risk for a brief tornado across much of the Marginal Risk
area. Consensus of latest model guidance indicates low/mid-level
flow will weaken somewhat this afternoon before gradually
re-intensifying this evening as the next embedded shortwave trough
and associated mid-level jet overspread coastal northern/central CA.
A mix of linear bands and cellular convective structures may
continue to pose an intermittent risk for isolated damaging gusts
and perhaps a brief tornado into this evening/tonight, before the
severe threat gradually diminishes towards 12Z early Friday morning.

..Gleason/Supinie.. 12/25/2025

$$

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ACUS01 KWNS 251940
SWODY1
SPC AC 251938

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0138 PM CST Thu Dec 25 2025

Valid 252000Z - 261200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
COASTAL CALIFORNIA AND THE CENTRAL VALLEY...

...SUMMARY...
An isolated risk for severe gusts/localized wind damage and perhaps
a brief tornado will be possible today into this evening along much
of the California Coast and portions of the Central Valley.

...20z Update...
The previous outlook reasoning remains on track, and no changes were
made with this update.

A few thunderstorms had developed over the Sacramento Valley since
18z, where partial clearing was noted and weak buoyancy (200-300
J/kg) was present. Offshore, an increase in lightning was noted as
the next upstream vorticity maximum moves towards the CA Coast.
Although buoyancy will remain weak, stronger low/mid-level flow will
become re-established later this afternoon/evening and will support
an isolated risk of strong/severe wind gusts with a few
stronger/sustained convective elements, and low-level hodographs
will be sufficiently curved to conditionally support a brief
tornado.

..Bunting.. 12/25/2025

.PREV DISCUSSION... /ISSUED 1026 AM CST Thu Dec 25 2025/

...California...
Recent satellite imagery shows a mid/upper-level low over the
eastern Pacific and a negative-tilt shortwave trough moving
northward along the northern CA and OR Coast. An upstream mid-level
jet and associated vorticity maximum will move through the base of
the eastern Pacific upper low/trough and approach the San Francisco
Bay and northern CA vicinity this evening.

Strong to locally severe thunderstorms capable of producing mainly
isolated severe/damaging winds will remain possible with convection
today into this evening. Weak instability is forecast to persist
across much of coastal CA into the Central Valley, with cool surface temperatures, saturated profiles, and modest lapse rates aloft
(reference the 12Z OAK sounding) limiting the development of greater
MUCAPE. Still, a favorable kinematic environment with enhanced west-southwesterly mid/upper-level flow will conditionally support
occasional strong to severe convection, contingent on sufficiently deep/sustained updraft development.

Low-level hodographs are forecast to remain enlarged enough to yield
a low risk for a brief tornado across much of the Marginal Risk
area. Consensus of latest model guidance indicates low/mid-level
flow will weaken somewhat this afternoon before gradually
re-intensifying this evening as the next embedded shortwave trough
and associated mid-level jet overspread coastal northern/central CA.
A mix of linear bands and cellular convective structures may
continue to pose an intermittent risk for isolated damaging gusts
and perhaps a brief tornado into this evening/tonight, before the
severe threat gradually diminishes towards 12Z early Friday morning.

$$

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ACUS01 KWNS 260027
SWODY1
SPC AC 260026

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0626 PM CST Thu Dec 25 2025

Valid 260100Z - 261200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ALONG MUCH OF
THE CALIFORNIA COAST AND INTO THE CENTRAL AND NORTHERN VALLEYS...

...SUMMARY...
The risk for isolated severe thunderstorms will persist this evening
and into tonight across much of the California Coast and portions of
the Central and Northern Valleys.

...Coastal CA into the Central and Northern Valleys...
Scattered showers and thunderstorms persist this evening from the
Sacramento Valley toward the central coastline, with another area
over southern CA. Areas of heating have led to a few stronger cells
around the Sacramento area, with indications of marginal hail. To
the west, another frontal band of convection will continue to
approach much of the central coastal counties. The 00Z OAK sounding
shows steep lapse rates and strong shear profiles, which may favor
both damaging gusts or embedded areas of rotation as leading cells
and/or the frontal band approach later this evening. As such, will
maintain the Marginal Risk.

For more information, see mesoscale discussion 2272.

..Jewell.. 12/26/2025

$$

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ACUS01 KWNS 260544
SWODY1
SPC AC 260542

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1142 PM CST Thu Dec 25 2025

Valid 261200Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not expected across the continental U.S. today.
General thunderstorm activity is most likely from lower Michigan
into Pennsylvania, and from parts of California into the Great
Basin.

...Synopsis and Discussion...
A slow-moving positive tilt upper trough will move across CA and
into the Great Basin through tonight, with a weakening surface low
dropping southeastward into northern CA. Modest southwest flow aloft
will support continued moist conditions with areas of more
concentrated rain and embedded thunderstorms. In general, veering
low-level winds and/or weak instability will likely preclude much of
a severe thunderstorm risk, though stronger gusts may occur
coincident with shallow convection in favored areas of terrain
across parts of CA.

To the east, a low-amplitude upper trough will move across the Great
Lakes and OH Valley during the day and toward the Mid Atlantic late,
with a plume of 50s F dewpoints surging into OH. Several hundred
J/kg elevated MUCAPE will develop, supporting scattered
thunderstorms. While deep-layer effective shear may support cellular
storm mode, generally weak instability levels are unlikely to
support severe hail.

..Jewell/Karstens.. 12/26/2025

$$

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ACUS01 KWNS 261222
SWODY1
SPC AC 261220

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0620 AM CST Fri Dec 26 2025

Valid 261300Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast across the contiguous United
States through tonight.

...Synopsis...
Water-vapor imagery this morning shows a large-scale upper trough
over the Pacific Northwest coast and eastern Pacific. This
positive-tilt trough will shift eastward to the northern Rockies and
Sierra Nevada by early Saturday morning. Concurrently, a flattened
mid to upper-level ridge over the Great Plains will move into the MS
Valley. Plume of subtropical moisture over the eastern Pacific will
continue to advect northeast into portions of the Interior West.
Showers and widely spaced, occasional thunderstorms are likely today
across CA into the Great Basin and northern Rockies. Scant
instability will likely preclude strong thunderstorm development
with this activity. Farther east, a few thunderstorms are possible
from the Great Lakes east-southeast into the northern Mid-Atlantic
states in advance of a mid-level shortwave trough forecast to move
east today.

..Smith/Weinman.. 12/26/2025

$$

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ACUS01 KWNS 261628
SWODY1
SPC AC 261626

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1026 AM CST Fri Dec 26 2025

Valid 261630Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast across the contiguous United
States through tonight.

...Synopsis and Discussion...
An upper trough will continue to progress eastward over the western
CONUS today. With cool temperatures at mid levels supporting weak
MUCAPE, isolated thunderstorms may occur across parts of CA into the
Great Basin and northern Rockies through the period as large-scale
ascent associated with the upper trough spreads inland. Mid-level
flow and related deep-layer shear should remain strong enough to
support some updraft organization across these areas, but limited
low-level moisture, cool surface temperatures, and overall weak
instability will likely hinder a meaningful severe threat from
materializing today. Elsewhere, isolated lightning flashes may occur
with elevated convection in a strong low-level warm advection regime
over portions of the Great Lakes into the Mid-Atlantic and southern
NY as a mid-level shortwave trough advances east-southeastward
across these areas.

..Gleason/Wendt.. 12/26/2025

$$

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ACUS01 KWNS 261948
SWODY1
SPC AC 261946

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0146 PM CST Fri Dec 26 2025

Valid 262000Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast across the contiguous United
States through tonight.

...20Z Update...
The general thunderstorm forecast was updated in the Lower Great
Lakes region on account of the shortwave trough progression. The
remainder of the forecast remains valid and is unchanged. See the
previous discussion for additional information.

..Wendt.. 12/26/2025

.PREV DISCUSSION... /ISSUED 1026 AM CST Fri Dec 26 2025/

...Synopsis and Discussion...
An upper trough will continue to progress eastward over the western
CONUS today. With cool temperatures at mid levels supporting weak
MUCAPE, isolated thunderstorms may occur across parts of CA into the
Great Basin and northern Rockies through the period as large-scale
ascent associated with the upper trough spreads inland. Mid-level
flow and related deep-layer shear should remain strong enough to
support some updraft organization across these areas, but limited
low-level moisture, cool surface temperatures, and overall weak
instability will likely hinder a meaningful severe threat from
materializing today. Elsewhere, isolated lightning flashes may occur
with elevated convection in a strong low-level warm advection regime
over portions of the Great Lakes into the Mid-Atlantic and southern
NY as a mid-level shortwave trough advances east-southeastward
across these areas.

$$

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ACUS01 KWNS 270046
SWODY1
SPC AC 270044

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0644 PM CST Fri Dec 26 2025

Valid 270100Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast through tonight.

...Discussion...
Scattered showers persist this evening from parts of CA into
northern UT, north of the midlevel jet with cool temperatures aloft.
With the loss of heating and in the absence of significant
large-scale ascent, a steady downward trend is expected through late
evening. Given weak instability coupled with a cooling boundary
layer, severe storms are unlikely.

To the east, a midlevel wave continues to move across the Mid
Atlantic, with scattered low-topped showers from WV across the warm
front into PA. The 00Z PIT sounding shows weak elevated instability
sufficient for a few lightning flashes with the larger batch of
precipitation as it pushes east across the remainder of PA, NJ, MD
and DE.

..Jewell.. 12/27/2025

$$

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ACUS01 KWNS 270526
SWODY1
SPC AC 270524

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1124 PM CST Fri Dec 26 2025

Valid 271200Z - 281200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Little thunderstorm activity is forecast across the contiguous U.S.
today. A few thunderstorms may occur from eastern Kansas into
northern Missouri toward Sunday morning.

...Synopsis and Discussion...
Most of the CONUS will remain free of thunderstorms for much of the
day as a western trough progresses into the Plains late tonight into
Sunday. Ahead of this trough, upper ridging will occur over the
MS/OH Valleys with low-level warming and moisture advection. Low 60s
F dewpoints will stream north out of the southern Plains and lower
MS Valley toward the lower MO/Mid MS Valley late. This air mass will
remain capped for most of the period.

After about 06Z tonight, midlevel cooling will be more prominent
into KS/NE/IA, with a zone of elevated instability becoming
uncapped. While effective shear will be strong, instability should
only average at or below 500 J/kg. CAMs suggest storms may develop
after 08Z over northeast KS and move into northern MO through 12Z
Sunday. It appears that any hail risk will be non-severe/small.

..Jewell/Karstens.. 12/27/2025

$$

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ACUS01 KWNS 271229
SWODY1
SPC AC 271228

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0628 AM CST Sat Dec 27 2025

Valid 271300Z - 281200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast through tonight across the
contiguous United States.

...Synopsis...
Water-vapor imagery this morning shows an upper trough over the
West. This upper feature will move east and reach the Dakotas and
central Rockies by early Sunday morning. Ahead of this trough,
upper ridging will occur over the MS/OH Valleys with a warm conveyor
focused over the lower MO Valley. Low 60s F dewpoints will stream
north out of the southern Plains and lower MS Valley toward the
lower MO/Mid MS Valley late and ahead of an approaching cold front
pushing southeast into the KS/IA vicinity.

Weak instability is forecast to gradually develop tonight over the
lower MO/mid MS Valley with an increase in showers and isolated
thunderstorms evolving primarily after midnight. Despite strong
effective shear, current thinking is storm intensity will be limited
with the elevated storm activity and hail potential will remain sub
severe.

..Smith/Weinman.. 12/27/2025

$$

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ACUS01 KWNS 271618
SWODY1
SPC AC 271616

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1016 AM CST Sat Dec 27 2025

Valid 271630Z - 281200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast through tonight across the
contiguous United States.

...Synopsis and Discussion...
A large-scale upper trough with multiple embedded perturbations will
move eastward from the western CONUS across much of the Plains
through the period. While cold mid-level temperatures will accompany
this upper trough, meager low-level moisture and cool surface
temperatures should generally limit instability and the potential
for lightning with any convective showers that can develop this
afternoon across the Great Basin/Rockies.

Low-level moisture will gradually return northward through tonight
across the lower/mid MS Valley and lower OH Valley ahead of a strong
cold front and deepening surface low over the central Plains and mid
MO Valley. Increasing warm/moist advection associated with a
low-level jet should eventually support weak MUCAPE and isolated
thunderstorm potential across parts of eastern KS into MO and
central IL late tonight/early Sunday morning. With MUCAPE forecast
to remain generally less than 750 J/kg, the potential for severe
hail with elevated convection appears low even though deep-layer
shear will be strong.

..Gleason/Wendt.. 12/27/2025

$$

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ACUS01 KWNS 271936
SWODY1
SPC AC 271934

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0134 PM CST Sat Dec 27 2025

Valid 272000Z - 281200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast through tonight across the
contiguous United States.

...20z Update...
The previous forecast remains on track with no changes required.
Latest high-res guidance continues to show limited thunderstorm
potential until around/after 06z tonight across portions of
northeast KS into northern MO and western IL. See the previous
discussion below for additional details.

..Moore.. 12/27/2025

.PREV DISCUSSION... /ISSUED 1016 AM CST Sat Dec 27 2025/

...Synopsis and Discussion...
A large-scale upper trough with multiple embedded perturbations will
move eastward from the western CONUS across much of the Plains
through the period. While cold mid-level temperatures will accompany
this upper trough, meager low-level moisture and cool surface
temperatures should generally limit instability and the potential
for lightning with any convective showers that can develop this
afternoon across the Great Basin/Rockies.

Low-level moisture will gradually return northward through tonight
across the lower/mid MS Valley and lower OH Valley ahead of a strong
cold front and deepening surface low over the central Plains and mid
MO Valley. Increasing warm/moist advection associated with a
low-level jet should eventually support weak MUCAPE and isolated
thunderstorm potential across parts of eastern KS into MO and
central IL late tonight/early Sunday morning. With MUCAPE forecast
to remain generally less than 750 J/kg, the potential for severe
hail with elevated convection appears low even though deep-layer
shear will be strong.

$$

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ACUS01 KWNS 280016
SWODY1
SPC AC 280015

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0615 PM CST Sat Dec 27 2025

Valid 280100Z - 281200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast through tonight across the
contiguous United States.

...Discussion...
Low pressure will shift eastward across KS tonight and into western
MO by Sunday morning, ahead of a cold front surging into the central
Plains. Southwesterly low-level winds will maintain warmth ahead of
the cold front, with dewpoints to around 60 F spreading northward
toward I-70 late. Increasing lift associated with the front and
approaching upper trough should instigate scattered thunderstorms
over northeast KS and into northern MO, primarily after 09Z.
Forecast soundings indicate elevated MUCAPE over 500 J/kg will
develop, while deep-layer effective shear remains strong. This may
yield a few stronger cells, possibly producing small hail, though
the most likely scenario is for hail to remain below severe levels.

..Jewell.. 12/28/2025

$$

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ACUS01 KWNS 280455
SWODY1
SPC AC 280454

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1054 PM CST Sat Dec 27 2025

Valid 281200Z - 291200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN
MISSOURI INTO WESTERN OHIO...

...SUMMARY...
Strong thunderstorms may develop over Missouri and Illinois today,
and move across parts of Indiana, Kentucky and Ohio through evening.
A few damaging wind gusts appear to be the primary severe threat.

...Synopsis...
An upper low will deepen as it moves from the northern Plains into
the upper Great Lakes, with rapidly intensifying mid and high level
flow and strong height falls spreading across much of the Midwest.
At the surface, low pressure will deepen from northern MO this
morning into Lower MI by 00Z, with an intense cold front trailing
southwest from the low. By mid afternoon, this front will extend
from northern IL into eastern MO and northwest AR, with southerly
winds aiding northward moisture transport with dewpoints near 60 F.
A warm front will lift across IL, IN, and southern Lower MI as the
low develops northeastward. Lift along these boundaries will support
scattered thunderstorms, with the greatest probabilities generally
near the surface low track from northeast MO into Lower MI. Given
strong wind fields, sporadic severe storms may occur.

...From MO into OH...
For the morning hours, scattered elevated thunderstorms appear
likely from eastern IA across northern IL, IN, and southern Lower MI
north of the warm front and in the zone of theta-e advection.
Forecast soundings indicate sufficient MUCAPE for perhaps small
hail.

From midday into the afternoon, SBCAPE over 500 J/kg is forecast
ahead of the cold front and near the surface low from eastern MO
across central IL and into IN. This is conditionally a favorable
area for supercells, though in this case the lack of surface heating
along with a cap below 700 mb suggest the bulk of the diurnal
convection should be relegated to the cold front, in which case a
linear mode seems likely. Still, given hodographs favoring
supercells, a few embedded areas of rotation will be possible and a
brief tornado cannot be ruled out. Otherwise, damaging winds will be
the primary concern

..Jewell/Squitieri.. 12/28/2025

$$

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ACUS01 KWNS 281302
SWODY1
SPC AC 281300

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0700 AM CST Sun Dec 28 2025

Valid 281300Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN
ILLINOIS TO INDIANA...

...SUMMARY...
Scattered severe thunderstorms are possible over Illinois and
Indiana this afternoon through the evening. Severe wind gusts
capable of wind damage and a couple of tornadoes are the primary
threats.

...Mid MS Valley east through IN-OH-western PA...
Water-vapor imagery this morning shows a mid-level low near the
MT/ND border with a trough into the central Rockies/Sangre de
Cristos. This mid-level low will move into the central Great Lakes
by early Monday morning. Strong southwesterly 500-mb flow (80 kt)
extending from the base of the trough through the lower MO Valley
and OH Valley will feature an intensifying 110-kt jet reaching the
MO-IL border this evening before further strengthening to 130 kt
over OH by the end of the period.

A surface low over eastern KS will deepen rapidly through tonight as
it moves to Lake Huron. A frontal zone extending east-northeast
through the southern Great Lakes this morning will serve as the
northern edge of the moist sector. A cold front initially over
KS-OK will surge south-east. Southerly low-level flow across the
moist sector will maintain a fetch of seasonably high 58-62 deg F
dewpoints immediately ahead of the front/low.

A rain shield with embedded thunderstorms this morning from northern
MO into the southern Great Lakes could feature a stronger storm or
two through midday, but the primary severe risk will likely focus
this afternoon through tonight. Model guidance indicates the cap
will erode near the evolving triple point and cold front by mid-late
afternoon. Upwards of 500-1000 J/kg MLCAPE is possible across parts
of central into eastern IL with buoyancy tapering with east extent
across the OH Valley. A southward-developing convective band is
forecast to evolve late this afternoon through the early evening.
Long hodographs and strong 2-3 km flow will favor a risk for severe
gusts with the more intense storms and surges with the maturing
band. Models indicate the wind-damage threat may persist across the
OH Valley/southern Great Lakes tonight despite meager instability.
The tornado risk appears highest with cells that can develop near
the instability axis and mature before either destructive
interference of the larger-scale cold pool overwhelms cellular mode,
and/or this activity moves farther east into lessening instability.

..Smith/Weinman.. 12/28/2025

$$

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ACUS01 KWNS 281641
SWODY1
SPC AC 281640

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1040 AM CST Sun Dec 28 2025

Valid 281630Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
EASTERN ILLINOIS INTO INDIANA AND WESTERN KENTUCKY...

...SUMMARY...
Scattered severe thunderstorms are possible over parts of the
Midwest and lower Ohio Valley this afternoon through the evening. Severe/damaging wind gusts and a couple of tornadoes are the primary
threats.

...Mid Mississippi Valley into the Midwest/Ohio Valley...
An upper trough/low over the northern Plains this morning will
further intensify today as it develops towards the Upper
Midwest/Great Lakes through the period. Pronounced large-scale
ascent associated with a strengthening mid/upper jet (100-120 kt at
500 mb) over the mid MS Valley into IL/IN will encourage rapid
deepening of a surface low as it develops from central/northern IL
into Lower MI by this evening. A rather moist low-level airmass with
generally upper 50s to low 60s surface dewpoints will continue to
spread northward across the mid MS Valley into parts of the
Midwest/OH Valley and southern Great Lakes regions in tandem with a northward-shifting surface warm front. A cold front is also expected
to sweep east-southeastward across these regions this
afternoon/evening as the surface low tracks northeastward. This cold
front should serve as a focus for strong to severe convection later
today.

The 12Z ILX sounding showed a moist but saturated profile through
much of the troposphere, with strong west-southwesterly
mid/upper-level winds already present over the warm sector. Current expectations are for ongoing, mostly elevated convection across
central IL to pose a threat for isolated hail and strong to locally
severe gusts given the strength of the mid-level flow. This activity
may linger along/just north the warm front through the afternoon as
it spreads quickly east-northeastward into IN. Additional
thunderstorms are expected to form along/near the cold front across
IL and vicinity by 20-22Z as modest/filtered daytime heating occurs,
with come cloud breaks already noted in visible satellite imagery
across east-central MO/south-central IL. It does appear that surface temperatures are warming faster/more than forecast by some guidance
across the warm sector in IL, with 16Z observations at some stations
already reaching into the upper 60s/low 70s.

The more aggressive 12Z guidance and recent RAP runs suggest that
around 500-1000 J/kg of MLCAPE may ultimately develop in a narrow
corridor across eastern IL and western IN/KY ahead of the front,
even though modest lapse rates aloft will likely inhibit more robust destabilization. This weak instability should be sufficient to
support organized updrafts, as both low-level and deep-layer shear
will be quite strong owing to the strengthening wind profiles across
the warm sector this afternoon/evening with the approaching
mid/upper-jet. There is still some uncertainty regarding the
potential for pre-frontal convection. But, any low-topped supercells
that can form and be sustained should pose a threat for a couple of
tornadoes with upwards of 200-250 m2/s2 of effective SRH present.
Eventual development of a thin/forced line of convection along the
cold front appears likely, with a threat for scattered
severe/damaging winds and perhaps a couple of embedded tornadoes. At
least an isolated severe threat may persist this evening/tonight
across the OH Valley and parts of western PA, where low-level flow
is forecast to remain quite strong even with minimal instability.

..Gleason/Wendt.. 12/28/2025

$$

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ACUS01 KWNS 281947
SWODY1
SPC AC 281946

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0146 PM CST Sun Dec 28 2025

Valid 282000Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF ILLINOIS...WESTERN KENTUCKY AND INDIANA...

...SUMMARY...
Scattered severe thunderstorms are possible over parts of the
Midwest and lower Ohio Valley this afternoon through the evening. Severe/damaging wind gusts and a couple of tornadoes are the primary
threats.

...20Z Update...
The only change to the outlook for this issuance is to trim the
Marginal Risk area across parts of north-central Illinois behind a
cold front that is moving southeastward across the region.

..Broyles.. 12/28/2025

.PREV DISCUSSION... /ISSUED 1040 AM CST Sun Dec 28 2025/

...Mid Mississippi Valley into the Midwest/Ohio Valley...
An upper trough/low over the northern Plains this morning will
further intensify today as it develops towards the Upper
Midwest/Great Lakes through the period. Pronounced large-scale
ascent associated with a strengthening mid/upper jet (100-120 kt at
500 mb) over the mid MS Valley into IL/IN will encourage rapid
deepening of a surface low as it develops from central/northern IL
into Lower MI by this evening. A rather moist low-level airmass with
generally upper 50s to low 60s surface dewpoints will continue to
spread northward across the mid MS Valley into parts of the
Midwest/OH Valley and southern Great Lakes regions in tandem with a northward-shifting surface warm front. A cold front is also expected
to sweep east-southeastward across these regions this
afternoon/evening as the surface low tracks northeastward. This cold
front should serve as a focus for strong to severe convection later
today.

The 12Z ILX sounding showed a moist but saturated profile through
much of the troposphere, with strong west-southwesterly
mid/upper-level winds already present over the warm sector. Current expectations are for ongoing, mostly elevated convection across
central IL to pose a threat for isolated hail and strong to locally
severe gusts given the strength of the mid-level flow. This activity
may linger along/just north the warm front through the afternoon as
it spreads quickly east-northeastward into IN. Additional
thunderstorms are expected to form along/near the cold front across
IL and vicinity by 20-22Z as modest/filtered daytime heating occurs,
with come cloud breaks already noted in visible satellite imagery
across east-central MO/south-central IL. It does appear that surface temperatures are warming faster/more than forecast by some guidance
across the warm sector in IL, with 16Z observations at some stations
already reaching into the upper 60s/low 70s.

The more aggressive 12Z guidance and recent RAP runs suggest that
around 500-1000 J/kg of MLCAPE may ultimately develop in a narrow
corridor across eastern IL and western IN/KY ahead of the front,
even though modest lapse rates aloft will likely inhibit more robust destabilization. This weak instability should be sufficient to
support organized updrafts, as both low-level and deep-layer shear
will be quite strong owing to the strengthening wind profiles across
the warm sector this afternoon/evening with the approaching
mid/upper-jet. There is still some uncertainty regarding the
potential for pre-frontal convection. But, any low-topped supercells
that can form and be sustained should pose a threat for a couple of
tornadoes with upwards of 200-250 m2/s2 of effective SRH present.
Eventual development of a thin/forced line of convection along the
cold front appears likely, with a threat for scattered
severe/damaging winds and perhaps a couple of embedded tornadoes. At
least an isolated severe threat may persist this evening/tonight
across the OH Valley and parts of western PA, where low-level flow
is forecast to remain quite strong even with minimal instability.

$$

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ACUS01 KWNS 290052
SWODY1
SPC AC 290050

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0650 PM CST Sun Dec 28 2025

Valid 290100Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MIDWEST AND OHIO VALLEY...

...SUMMARY...
Scattered severe thunderstorms remain possible over parts of the
Midwest and Ohio Valley this evening. Severe/damaging wind gusts and
perhaps a tornado are the primary threats.

...01z Update...

Midlevel low is digging southeast across southeast SD early this
evening. This feature is forecast to track across IA then eject into
northern lower MI by the end of the period as an intense 500mb speed
max translates into the OH Valley. In response to this short wave,
surface low will deepen as it lifts north across lower MI overnight.
The primary concern for deep convection, especially this evening,
will be along the cold front as it surges across IN/western KY.
Latest radar data exhibits a narrow, strongly forced line of
convection from near Fort Wayne, IN southwest across southern IL
into extreme northeast AR. This activity has progressed through the
primary corridor of instability, but pre frontal air mass across the
OH Valley remains adequately buoyant for surface-based convection,
at least for the next several hours. Damaging winds should be the
primary risk this evening, though a tornado or two can not be ruled
out.

..Darrow.. 12/29/2025

$$

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ACUS01 KWNS 290523
SWODY1
SPC AC 290521

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1121 PM CST Sun Dec 28 2025

Valid 291200Z - 301200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few thunderstorms may be noted across the lower Rio Grande Valley
very early in the period.

...Lower Rio Grande Valley...

Surface front is surging south across south central TX late this
evening as pressures build over the central/southern Plains. Latest
model guidance suggests the wind shift will reach the international
border around 12z, then quickly advance deep into northeast Mexico.
A narrow band of shallow convection is currently noted along the
front as far west as Wilson county TX. Forecast soundings for deep
South TX at the start of the period suggest both pre frontal and
post frontal parcels will exhibit sufficient buoyancy for the
strongest updrafts to possibly penetrate levels necessary for
lightning discharge. Any post frontal lightning threat should be
over by 15z.

..Darrow/Squitieri.. 12/29/2025

$$

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ACUS01 KWNS 291247
SWODY1
SPC AC 291245

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0645 AM CST Mon Dec 29 2025

Valid 291300Z - 301200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms will not occur across the contiguous United
States through tonight.

...Synopsis...
Water-vapor imagery this morning shows a trough over the Great Lakes
and much of the eastern U.S. whereas a split-flow pattern prevails
over the West. A cold front will continue south through much of the
Gulf of America and move east of the Eastern Seaboard during the
period. High pressure centered over the south-central states will
lead to cool/stable conditions over much of the Lower 48.

..Smith/Weinman.. 12/29/2025

$$

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ACUS01 KWNS 291601
SWODY1
SPC AC 291600

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1000 AM CST Mon Dec 29 2025

Valid 291630Z - 301200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...Synopsis and Discussion...
An amplified upper trough/low with an intense mid-level jet will
continue advancing east-northeastward over Ontario/Quebec and the
eastern CONUS today. A related strong surface cold front will also
move east-southeastward across the Southeast and Gulf through the
period. With negligible instability forecast over land ahead of the
front, thunderstorm probabilities still appear less than 10%.

..Gleason/Wendt.. 12/29/2025

$$

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ACUS01 KWNS 291937
SWODY1
SPC AC 291935

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0135 PM CST Mon Dec 29 2025

Valid 292000Z - 301200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast in the U.S. through tonight.

...DISCUSSION...
No changes are made to the outlook for this issuance.

..Broyles.. 12/29/2025

.PREV DISCUSSION... /ISSUED 1000 AM CST Mon Dec 29 2025/

...Synopsis and Discussion...
An amplified upper trough/low with an intense mid-level jet will
continue advancing east-northeastward over Ontario/Quebec and the
eastern CONUS today. A related strong surface cold front will also
move east-southeastward across the Southeast and Gulf through the
period. With negligible instability forecast over land ahead of the
front, thunderstorm probabilities still appear less than 10%.

$$

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ACUS01 KWNS 300019
SWODY1
SPC AC 300017

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0617 PM CST Mon Dec 29 2025

Valid 300100Z - 301200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast tonight.


..Darrow.. 12/30/2025

$$

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ACUS01 KWNS 300519
SWODY1
SPC AC 300517

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1117 PM CST Mon Dec 29 2025

Valid 301200Z - 311200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast.


..Darrow/Squitieri.. 12/30/2025

$$

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ACUS01 KWNS 301222
SWODY1
SPC AC 301221

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0621 AM CST Tue Dec 30 2025

Valid 301300Z - 311200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

The absence of appreciable instability across the CONUS will
preclude thunderstorm development through tonight.

..Bunting/Weinman.. 12/30/2025

$$

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ACUS01 KWNS 301602
SWODY1
SPC AC 301600

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1000 AM CST Tue Dec 30 2025

Valid 301630Z - 311200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...Synopsis and Discussion...
With cool/stable conditions prevalent behind a cold front across a
large portion of the CONUS, thunderstorms are not forecast today.

..Gleason/Wendt.. 12/30/2025

$$

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ACUS01 KWNS 301924
SWODY1
SPC AC 301923

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0123 PM CST Tue Dec 30 2025

Valid 302000Z - 311200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...Synopsis...

No changes are needed with the 20z Day 1 Update. Thunderstorm
activity is not expected through tonight/early Wednesday.

..Leitman.. 12/30/2025

.PREV DISCUSSION... /ISSUED 1000 AM CST Tue Dec 30 2025/

...Synopsis and Discussion...
With cool/stable conditions prevalent behind a cold front across a
large portion of the CONUS, thunderstorms are not forecast today.

$$

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ACUS01 KWNS 310022
SWODY1
SPC AC 310020

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0620 PM CST Tue Dec 30 2025

Valid 310100Z - 311200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast.


..Darrow.. 12/31/2025

$$

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ACUS01 KWNS 310515
SWODY1
SPC AC 310513

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1113 PM CST Tue Dec 30 2025

Valid 311200Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible along coastal southern
California very late in the period.

...Southern CA...

Seasonally strong southern-stream upper trough is forecast to
approach the southern CA coast late in the period. Latest model
guidance suggests a strong 500mb speed max will translate through
the base of the trough by 01/12z, and the left-exit region of this
speed max will encourage convection along/ahead of a weak front as
it surges inland, primarily after 09z. Forecast soundings along the
coast suggest thunderstorms should be elevated in nature, with
initial convection likely rooted above 850mb. However, as the front
approaches, the level of parcel lift should lower, but likely remain
slightly elevated. Even so, low-level shear/forcing is not expected
to be particularly strong, and buoyancy appears inadequate for any
meaningful risk of severe.

..Darrow/Squitieri.. 12/31/2025

$$

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ACUS01 KWNS 311226
SWODY1
SPC AC 311225

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0625 AM CST Wed Dec 31 2025

Valid 311300Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible along coastal southern
California very late in the period.

...Southern CA...
A southern-stream upper-level trough will approach the southern CA
coast late tonight. Latest model guidance suggests increasing
large-scale ascent will approach the coast, contributing to isolated
convection along/ahead of a weak front as it surges inland,
primarily after 09z. Forecast soundings along the coast suggest
thunderstorms should be elevated in nature, with initial convection
likely rooted at or above 850mb. Weak buoyancy and shear suggests
minimal potential for severe storms prior to 12z Thursday.

..Bunting/Weinman.. 12/31/2025

$$

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ACUS01 KWNS 311612
SWODY1
SPC AC 311610

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1010 AM CST Wed Dec 31 2025

Valid 311630Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms may occur across parts of southern California
late tonight into early Thursday morning.

...Synopsis and Discussion...
With upper ridging remaining prominent over the western CONUS and
upper troughing centered across the eastern states, thunderstorm
potential should remain minimal though tonight for a large majority
of the CONUS. One exception will be across parts of southern CA late
tonight into early Thursday morning, as an upper trough/low over the
eastern Pacific gradually approaches the CA Coast by the end of the
period. While low-level moisture and related instability are both
expected to remain limited, increasing large-scale ascent and
gradually cooling mid-level temperatures preceding the upper
trough/low may still support isolated convection capable of
producing occasional lightning flashes, mainly after 01/06Z. Both
MUCAPE and deep-layer shear appear too weak to support a meaningful
threat for organized severe thunderstorms through the end of the
period (12Z Thursday morning).

..Gleason/Wendt.. 12/31/2025

$$

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ACUS01 KWNS 311955
SWODY1
SPC AC 311954

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0154 PM CST Wed Dec 31 2025

Valid 312000Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms may occur across parts of southern California
late tonight into early Thursday morning.

...20Z Update Discussion...
No changes are made to the outlook for this issuance.

..Broyles.. 12/31/2025

.PREV DISCUSSION... /ISSUED 1010 AM CST Wed Dec 31 2025/

...Synopsis and Discussion...
With upper ridging remaining prominent over the western CONUS and
upper troughing centered across the eastern states, thunderstorm
potential should remain minimal though tonight for a large majority
of the CONUS. One exception will be across parts of southern CA late
tonight into early Thursday morning, as an upper trough/low over the
eastern Pacific gradually approaches the CA Coast by the end of the
period. While low-level moisture and related instability are both
expected to remain limited, increasing large-scale ascent and
gradually cooling mid-level temperatures preceding the upper
trough/low may still support isolated convection capable of
producing occasional lightning flashes, mainly after 01/06Z. Both
MUCAPE and deep-layer shear appear too weak to support a meaningful
threat for organized severe thunderstorms through the end of the
period (12Z Thursday morning).

$$

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ACUS01 KWNS 010054
SWODY1
SPC AC 010052

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0652 PM CST Wed Dec 31 2025

Valid 010100Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms may occur across parts of southern California
late tonight.

...01z Update...

Well-defined upper low is lifting northeast toward the southern CA
coast as a 500mb speed max translates into the base of the trough,
but remaining offshore. Left exit region of this jet will encourage
convection along the weak front as it surges toward the coast late
tonight. Primary concern for lightning will be after 09z, but this
activity will be elevated and within a poor instability environment.
Severe risk appears minimal tonight.

..Darrow.. 01/01/2026

$$

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ACUS01 KWNS 010532
SWODY1
SPC AC 010530

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1130 PM CST Wed Dec 31 2025

Valid 011200Z - 021200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF SOUTHERN COASTAL CALIFORNIA...

...SUMMARY...
Locally damaging winds, and a perhaps a brief weak tornado, could
occur along a portion of coastal southern California.

...Southern CA...

Latest water-vapor imagery depicts a well-defined upper low about
300 mi WSW of Lompoc CA ejecting ENE in line with latest model
guidance. This feature is forecast to shift inland as a 500mb speed
max translates across the Channel Islands toward southern NV by
early evening. Left-exit region of this jet will overspread the
southern interior valley with seasonally cool 500mb temperatures
noted north of the jet. Even so, forecast instability is expected to
remain weak as MUCAPE values should remain generally less than a few
hundred J/kg. Midlevel lapse rates are also not expected to be
particularly steep and this is reflected in the sparsity of
lightning currently noted with convection beneath the offshore low.

Latest thinking is scattered weak convection will be the primary
concern with the frontal zone early in the period, and much of this
activity may struggle to generate lightning despite the maritime
influences that will prove instrumental for this activity. While
some risk for gusty winds, and perhaps a brief weak tornado exists,
the majority of convection will remain sub severe.

..Darrow/Squitieri.. 01/01/2026

$$

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