Mesoscale Discussion 0708
   NWS Storm Prediction Center Norman OK
   0508 PM CDT Mon May 20 2019

   Areas affected...Portions of Texas South Plains into the Big Bend

   Concerning...Severe potential...Watch possible 

   Valid 202208Z - 210015Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Thunderstorms have initiated along the dryline west of
   Midland, TX. Storms will pose a large hail and severe wind gust
   threat, though the tornado threat should increase as storms move
   northeast. Farther south, initiation is more uncertain. Large hail
   and damaging wind gusts will be possible with any development. A new
   watch may be needed for new activity south of WW 197.

   DISCUSSION...Visible satellite imagery shows development of
   thunderstorms along the dryline west of Midland, TX with large
   MLCAPE values nearing 3000-3500 J/kg downstream. Initially, these
   storms will likely pose a threat for very large hail -- long
   straight hodographs per KMAF VAD and 18Z MAF sounding showing around
   8 C/km mid-level lapse rates -- a severe wind gust threat given the
   somewhat high surface dewpoint depressions. However, with time
   storms will progress northeast as continued low-level theta-e occurs
   and the 850 mb jet increases. RAP forecast soundings show improved
   low-level hodograph curvature that would support an increase in the
   tornado threat into the evening.

   Farther south near the Big Bend, some CAM guidance shows new
   thunderstorm development later this evening. Though initiation is a
   bit more uncertain here, the cumulus development along the higher
   terrain across the international border gives evidence to support
   this scenario. However, surface dewpoint depressions in this region
   are a bit larger. Large hail and severe wind gusts will likely be
   the primary threats, though a tornado cannot be ruled out should any
   potential development can tap into richer boundary layer moisture to
   the east.

   An extension of WW 197 will cover the threat in the MAF CWA. A new
   watch may be needed should storm initiation become more certain
   across the Big Bend and vicinity.

   ..Wendt/Guyer.. 05/20/2019

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

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

   LAT...LON   31440261 31990233 32050157 31370107 30230106 29920160
               29830215 30000254 30990269 31440261