Storm Prediction Center Mesoscale Discussion 925

   Mesoscale Discussion 0925
   NWS Storm Prediction Center Norman OK
   0553 PM CDT Wed May 21 2025

   Areas affected...Deep South TX

   Concerning...Severe potential...Watch unlikely 

   Valid 212253Z - 220100Z

   Probability of Watch Issuance...20 percent

   SUMMARY...A couple slow-moving storms may become sustained across a
   part of Deep South Texas, with an accompanying threat of large hail
   and localized severe gusts.

   DISCUSSION...Incipient convective development appears to be underway
   over Zapata and Jim Hogg counties, along an earlier differential
   heating corridor that is now covered by a cirrus canopy from nearly
   stationary thunderstorms over Nuevo Leon. With weak winds in the
   lowest 4 km per forecast soundings and CRP VWP data, along with
   nebulous large-scale ascent, sustaining organized updrafts is
   uncertain. Adequate speed shear does exist in the upper portion of a
   very large buoyancy profile. With already sustained convection over
   Nuevo Leon unlikely to spread across the border in the next few
   hours, the severe threat in Deep South TX will probably remain
   localized through at least mid-evening. Still, any sustained
   convection will pose a threat for large hail and downbursts given
   the degree of instability.

   ..Grams/Hart.. 05/21/2025

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...CRP...BRO...

   LAT...LON   26859937 27269917 27409866 27389839 27249826 27059806
               26499784 25979818 26429916 26859937 

   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN