ACUS01 KWNS 051250
SWODY1
SPC AC 051248

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0648 AM CST Sun Jan 05 2025

Valid 051300Z - 061200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE LOWER MISSISSIPPI VALLEY...

...SUMMARY...
Severe thunderstorms are expected this afternoon and evening from
the Sabine River Valley into the Mid-South and lower Mississippi
Valley. Tornadoes and scattered severe/damaging winds should be the
primary threats. A couple of strong tornadoes may also occur.

...East Texas into the Mid-South and Lower Mississippi Valley...
A strong shortwave trough over the central/southern High Plains this
morning will evolve into a closed upper low later today over eastern
KS/western MO. Related mid-level height falls and large-scale ascent
will encourage the primary surface low over central OK to develop
eastward to the Mid-South vicinity by late afternoon/early evening.
An attendant cold front will continue to sweep east-southeastward
over the southern Plains and lower MS Valley/Southeast through
tonight. Pronounced low-level mass response, with a 45-60 kt
low-level jet, will aid in the northward transport of partially
modified Gulf moisture across east TX and the lower MS Valley ahead
of the surging cold front.

Even though low/mid-level lapse rates are forecast to generally
remain modest, low to mid 60s surface dewpoints should be present by
early afternoon in a narrow corridor along and just ahead of the
cold front from parts of east TX to northern MS and vicinity.
Filtered daytime heating should support around 500-1000 J/kg of
MLCAPE by mid afternoon, with weaker instability with northward
extent into western TN near the surface low. Ample deep-layer shear
(40-50 kt) will be present across the warm sector to support
organized severe convection, including the potential for some
supercells. Current expectations are for surface-based convection to
develop and corresponding severe threat to increase in the early to
mid afternoon as the boundary layer gradually destabilizes. Given
the forcing of the cold front itself, a line of convection is
expected to eventually consolidate and pose a threat for mainly
scattered severe/damaging winds and a few tornadoes as it moves
quickly eastward through the early evening.

However, most high-resolution guidance shows some chance for
thunderstorms to develop along a weak surface trough/confluence zone
ahead of the front early this afternoon from parts of
central/northern LA into western MS. The strong low-level jet will
support enhanced low-level shear (effective SRH around 200-350+
m2/s2), and a threat for tornadoes with any supercells that can
mature in the narrow warm sector ahead of the surging cold front.
Given the rather favorable shear and enlarged low-level hodographs
shown in 06Z NAM/11Z RAP forecast soundings, a couple of strong
(EF-2) tornadoes appear possible with any sustained supercell across
this region. The best time frame for this tornado potential should
be mainly around 19-23Z, before any pre-frontal convection becomes
absorbed within the line. Isolated hail may also occur with this
activity. Embedded/QLCS tornadoes and damaging winds will still
remain possible for as long as the line can remain surface based.
Severe potential should quickly diminish with the line late this
evening and overnight as it continues into AL and encounters a less
favorable thermodynamic environment.

..Gleason/Bentley.. 01/05/2025

$$
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ACUS01 KWNS 051943
SWODY1
SPC AC 051942

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0142 PM CST Sun Jan 05 2025

Valid 052000Z - 061200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE LOWER MISSISSIPPI VALLEY...

...SUMMARY...
Severe thunderstorms remain possible this afternoon and evening from
the Sabine River Valley into the Mid-South and central Gulf Coast
states. Tornadoes and scattered damaging gusts remain the primary
threats. A couple of strong tornadoes may still occur.

...20Z Update...
The primary change to this outlook was to trim thunder/severe
probabilities from the west given the rapid eastward advancement of
the mid-level trough, and corresponding surface cold front,
progressing across the central MS Valley. Low-level moisture
advection continues across the Lower MS Valley as a 50+ kt low-level
jet remains in place, contributing to marginal instability (500-1000
J/kg MLCAPE), and strong low-level shear (evident via sizable,
curved hodographs and accompanying 300+ m2/s2 0-1 km SRH per recent
regional VADs). As such, any supercell or QLCS segment that can
intensify and become sustained in the warm sector (especially near
or just south of the warm front over central LA/MS) may produce
damaging gusts and/or tornadoes. The best chance for a strong
tornado this afternoon or evening will be with discrete supercells
ahead of the main band of cold frontal thunderstorms. Storms are
still expected to outpace the warm sector somewhere in AL, where a
decrease in severe potential is likely later this evening. Please
see MCDs 11 and 12 for more short-term severe weather information.

..Squitieri.. 01/05/2025

.PREV DISCUSSION... /ISSUED 0938 AM CST Sun Jan 05 2025/

...Synopsis...
Water-vapor imagery this morning shows a mid- to upper-level trough
over the central U.S. A powerful mid-level shortwave trough will
move through the base of the larger-scale trough over OK and move
into the lower OH Valley/Mid South with an accompanying 100-kt 500mb
speed max over the central Gulf Coast states by early Monday
morning. In the low levels, a cyclone over northeast OK will
develop east into the KY/TN border region late. An accompanying
cold front over the southern Great Plains this morning will sweep
southeastward into the lower MS Valley by late afternoon before
moving into the southern Appalachians and FL Panhandle by daybreak Monday.

...East Texas into the Mid-South and central Gulf Coast states...
A weak thunderstorm band this morning from western AR into northeast
TX has developed immediately ahead of the front in response to
intensifying large-scale ascent and strong low-level warm/moist
advection. Despite a pronounced capping inversion noted on the 12z
Shreveport, LA raob, additional moistening/destabilization and
ascent will promote additional storm development late this morning
into the afternoon. Model guidance shows only weak elevated
instability over northeast AR into western TN, but larger buoyancy
will exist over southern AR/LA/east TX where 500-1000 J/kg MLCAPE is
expected. Model forecast soundings show enlarged hodographs across
the surface-based warm sector with 0-1 km SRH generally in the
250-500 m2/s2 range. It appears a mix of pre-frontal and frontal
thunderstorm activity will evolve late this morning through the
early evening. The stronger and more persistent updrafts ahead of
the front will likely become supercellular and pose a risk for
tornadoes, including the possibility for strong tornadoes. Damaging
gusts and perhaps some tornado risk will likely evolve with the
frontal convection (QLCS) as it gradually intensifies this afternoon
and likely persists across the coastal plain through tonight. Have
increased low-severe probabilities farther east into southeast AL
where model guidance shows weak destabilization prior to frontal
passage late tonight.

$$
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