Storm Prediction Center Mesoscale Discussion 1020

   Mesoscale Discussion 1020
   NWS Storm Prediction Center Norman OK
   1138 PM CDT Tue May 27 2025

   Areas affected...Deep South TX

   Concerning...Severe potential...Severe Thunderstorm Watch likely 

   Valid 280438Z - 280645Z

   Probability of Watch Issuance...80 percent

   SUMMARY...A severe wind and hail threat should develop across parts
   of Deep South Texas as a thunderstorm cluster spreads east-southeast
   from Coahuila during the early morning. The short-term threat, while
   predominantly consisting of isolated severe coverage, should be
   sufficient to warrant overnight Severe Thunderstorm Watch issuance.

   DISCUSSION...A deep convective cluster is ongoing over northeast
   Coahuila. It has recently accelerated eastward to a forward speed of
   30 kts and should affect a portion of the Lower Rio Grande Valley in
   the next 1-2 hours. Large buoyancy still persists ahead of this
   cluster with only weak MLCIN where mid 80s surface temperatures
   persist along the valley. Farther east, richer moisture but cooler
   temperatures renders some uncertainty on how far east an organized
   severe threat should extend. But with east-southeasterly low-level
   winds veering to moderate upper-level westerlies, several hours of
   severe threat appears probable. There are signals that additional
   storms may develop ahead of this cluster, which could result in a
   broader MCS in the pre-dawn hours towards the coast.

   ..Grams/Mosier.. 05/28/2025

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

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

   LAT...LON   28640041 28609973 28479871 28299811 27869748 27319742
               26949783 26799816 26859881 27129940 27609973 28640041 

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