Mesoscale Discussion 0647
   NWS Storm Prediction Center Norman OK
   0619 PM CDT Wed May 20 2020

   Areas affected...portions of southern Texas

   Concerning...Severe potential...Watch unlikely 

   Valid 202319Z - 210115Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Isolated storms will pose a threat for hail and wind as
   they slowly move east and cross the Rio Grande in the Del Rio, TX
   vicinity. A watch is not likely due to the isolated threat.

   DISCUSSION...Storms developing off the higher terrain of the Sierra
   del Carmen mountains in northern Mexico will continue gradually
   propagating east over the Rio Grande near Del Rio, TX in the next
   few hours. Although deep layer wind shear is weak (effective bulk
   wind shear near 20 knots) and outrunning outflows have been noted
   from KDFX, moderate MLCAPE values between 3000-3500 J/kg suggest
   that severe hail will be possible with any robust updraft that
   develops along the periphery/outflow of existing convection.
   Low-level lapse rates between 7-8 C/km in the 0-1 km layer may allow
   for some evaporative cooling and downdraft acceleration that could
   lead to damaging winds. While individual storms should be
   short-lived, additional development along outflows should continue
   for the next few hours before loss of daytime heating and boundary
   layer stabilization inhibits lift along any outflow boundary. Due to
   the isolated nature of the threat, a watch is not likely.

   ..Moore/Thompson.. 05/20/2020

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

   ATTN...WFO...EWX...MAF...

   LAT...LON   29900171 30080110 29900055 29340005 28650003 28450044
               28480105 28840180 29390194 29900171