Severe Storm Outlook Narrative (AC)
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ACUS01 KWNS 260042
SPC AC 260041

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0741 PM CDT Wed Apr 25 2018

Valid 260100Z - 261200Z


Isolated strong to severe thunderstorms may continue to affect parts
of south Texas this evening.

...South Texas...
The latest water vapor imagery shows an upper-level low over the
central states with an upper-level trough extending southwestward
into the southern Plains. The southern extension of the trough is
located across the lower Rio Grande Valley and a plume of mid-level
moisture is present ahead of the trough along the Texas Coastal
Plain. Scattered thunderstorms are ongoing within this plume along a
corridor of instability. The RAP is analyzing this corridor of
instability across the western part of south Texas where MLCAPE
values are estimated in the 250 to 500 J/kg range. In addition, the
00Z soundings at Corpus Christi and Brownsville both have 45 to 50
kt of 0-6 km shear with some directional shear in the lowest 3 km
AGL. This combined with steep mid-level lapse rates around 7.5 C/km
may be enough to continue a marginal severe threat for a couple more
hours. However, as storms approach the lower Texas Coast this
evening where instability is considerably weaker, convection should
gradually weaken.

..Broyles.. 04/26/2018

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