Mesoscale Discussion 0656
   NWS Storm Prediction Center Norman OK
   0613 PM CDT Mon May 17 2021

   Areas affected...South TX

   Concerning...Severe potential...Watch possible 

   Valid 172313Z - 180045Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Intense thunderstorm development is possible this evening
   along an outflow boundary. A conditional threat for very large hail,
   locally damaging wind, and a tornado or two will be present with any
   supercell that develops.

   DISCUSSION...At 23Z, convective initiation appears to be underway
   across Dimmit County TX. This development is along a remnant outflow
   boundary, with very hot conditions south of the boundary and very
   warm/moist conditions noted north of the boundary. Extreme
   instability (MLCAPE approaching 4000 J/kg) and sufficient effective
   shear (35-45 kt) would support supercell development with any mature
   convection in the area. Very large hail would be the primary initial
   threat, though a tornado would also be possible, given the presence
   of very large CAPE in the vicinity of the boundary, where low-level
   shear is locally maximized. Watch issuance may be required soon.

   ..Dean/Grams.. 05/17/2021

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

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

   LAT...LON   28700042 28760006 28689932 28269877 27999875 27499953
               27609968 27759978 27940011 28210034 28570048 28700042