ACUS11 KWNS 050051
SWOMCD
SPC MCD 050051
NMZ000-AZZ000-050245-

Mesoscale Discussion 1834
NWS Storm Prediction Center Norman OK
0751 PM CDT Tue Aug 04 2026

Areas affected...southeastern Arizona

Concerning...Severe Thunderstorm Watch 538...

Valid 050051Z - 050245Z

The severe weather threat for Severe Thunderstorm Watch 538
continues.

SUMMARY...Thunderstorm activity appears likely to continue to
increase, particularly to the east and south of Tucson, through 7-9
PM MST, accompanied by occasional strong to severe outflow surface
gusts.

DISCUSSION...Deep-layer mean flow across the southern Arizona/New
Mexico state border vicinity and international border remains light
and northeasterly, but mid-level flow (around 20 kt near 500 mb)
appears a bit stronger with a more prominent easterly component than
24 hours ago.

A substantive clustering of storms, which has been propagating
slowly westward off the higher terrain to the north and northeast of
Safford, has shown notable recent weakening after becoming fairly
vigorous. It seems unlikely that it will make it to the lower
deserts, where the hot and deeply mixed boundary-layer remains
characterized by rather weak instability. However, based on latest mesoanalysis, boundary-layer instability east and south of the the
Tucson vicinity may be sufficient to maintain continuing convective
development and a southwestward propagation of the southern flank of
the cold pool over the next few couple of hours.

Later this evening, as outflow emanating from an evolving cluster
south of the international border interacts with the outflow
approaching from the northeast, there appears potential for
increasing thunderstorm development across the international border
vicinity near/south of Tucson. If this occurs, it appears that
low-level thermodynamic profiles may still be conducive to strong to
severe outflow surface gusts.

..Kerr.. 08/05/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fjg!4Jmc85uBSLnjnunnQ-HYSi6935dcNB0mKXETbyw3qh3xx5phMQnAVo7Rr1TyuXLiC7QdZTOEsuYlQBbLkau3_dnKl3w$ for graphic product...

ATTN...WFO...EPZ...TWC...

LAT...LON 31960873 31480901 30850917 30070952 30091036 31001148
31821153 32001038 32331018 32710998 32690968 32290934
31960873

MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN


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