SPC May 26, 2025 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1145 AM CDT Mon May 26 2025

Valid 261630Z - 271200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS TEXAS
EDWARDS PLATEAU/SOUTH-CENTRAL TEXAS...

...SUMMARY...
Severe thunderstorms are expected from parts of the southern Plains
eastward into the lower Mississippi Valley. Very large hail is
possible in parts of west-central/south-central Texas including the
Edwards Plateau/Hill Country, with severe/damaging winds becoming a
greater concern this afternoon/evening.

...Texas Edwards Plateau/Hill Country and South-central Texas...
Post-MCS outflow continues to settle southward across
south-central/southeast Texas at midday. Strong daytime heating is
anticipated across west-central Texas including the Edwards Plateau
vicinity as a weak upper trough moves slowly eastward across the
southern/central Plains through this evening. The front and stalling
composite outflow boundary will influence anticipated deep
convective development later today. Strong to locally extreme
instability will likely develop by peak afternoon heating, with
steep mid-level lapse rates contributing to this ample buoyancy.

Current expectations are for multiple thunderstorms to initiate
later this afternoon along/near the boundaries across the Concho
Valley/eastern Permian Basin and Edwards Plateau and quickly become
severe. Although low-level winds are forecast to remain modest,
mid/upper-level west-southwesterly flow gradually strengthening with
height should support around 40-50 kt of effective bulk shear. This
will easily foster intense supercells with the initial development
this afternoon, and large to very large hail (some 2+ inches in
diameter) appears likely. Some tornado potential will exist as well.
With time, clustering/upscale growth is anticipated as thunderstorms
spread east-southeastward toward the Hill Country and I-35 corridor
with an increasing severe wind potential into this evening.

...Lower Mississippi Valley/Southeast...
A well-organized convective line extends late this morning across
the ArkLaMiss into southwest Louisiana, which the most
organized/strongest portion of the line coincident with areas
along/north of a modifying residual boundary as a byproduct of
yesterday's convection. Damaging wind potential may modestly
increase as the boundary layer diurnally warms. For additional
details, see Mesoscale Discussion 988. 

Some guidance, particularly multiple recent NAM runs (but even RAP
to some extent), is insistent that the MCV near the ArkLaTex will
maintain its integrity through the day into tonight, with a related
east-northeastward transition over the ArkLaMiss toward the
Tennessee Valley in vicinity of the old synoptic front. MCS aside,
an MCV-related enhanced low/mid-level flow field could influence
some supercell/tornado potential later today across Mississippi into
Alabama, although prior-day outflow/convective overturning and
existing convection are major points of uncertainty for such
potential.

...Southern/Central High Plains...
A modest low-level upslope flow regime will persist today across
parts of the southern/central High Plains to the north of a surface
front. While instability should remain limited, isolated to widely
scattered convection should initially develop over the higher
terrain, before subsequently spreading eastward across the adjacent
High Plains through the afternoon/evening. Occasional large hail and
winds may occur with this activity, with some guidance suggesting a
small cluster may eventually develop this evening across eastern New
Mexico into northwest Texas. This scenario will be reevaluated into
mid-afternoon for any potential Slight Risk upgrade.

..Guyer/Lyons.. 05/26/2025

Read more