Thunderstorms have developed just west of Del Rio over the last hour. Unlike farther north in the Concho Valley, these locations are already south of the warm front. That means instability and wind shear values support organized surface-based supercelluar storm modes, even at this early hour. If these thunderstorms show signs of intensfying they could become severe with a risk of very large hail, localized damaging wind gusts, and even the threat of tornadoes. A tornado watch may be needed for the Edwards Pleateau by 2-3AM if these trends continue.

Mesoscale Discussion 0312
   NWS Storm Prediction Center Norman OK
   1256 AM CDT Sat Apr 13 2019

   Areas affected...portions of west Texas and the Rio Grande Valley

   Concerning...Severe potential...Watch possible

   Valid 130556Z - 130800Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Convection across western and southern portions of the
   discussion area should continue to strengthen, with potential for
   all modes of severe.  A Tornado Watch is being considered for the
   area.

   DISCUSSION...Convection continues to deepen across eastern
   Pecos/Terrell counties and just south of the Rio Grande near Del
   Rio.  These storms were already demonstrating supercellular
   characteristics, and these trends should continue given strongly
   vertically veering wind profiles, strong low-level shear (30-40
   kts), and moderate surface-based instability (mid-50s to low 60s F
   dewpoints beneath steep mid-level lapse rates and cooling aloft).
   Point forecast soundings indicate that any remaining cap across
   western/southern portions of the discussion has been mostly removed,
   and with continued low-level upslope against higher terrain in
   northern Mexico and lift associated with the approaching mid-level
   trough in New Mexico, convection should continue to expand over time
   and possibly necessitate a tornado watch across portions of the
   discussion area.  If issued, this watch will extend north of the
   current position of the warm front (subjectively analyzed from near
   6R6 to near JCT), with the expectation that this front should slowly
   migrate northward over time.

   Mid-level capping is a bit more pronounced in point forecast
   soundings in the eastern half of the discussion area (nearer San
   Antonio).  A couple of factors suggest presence of a severe threat
   in these areas beyond the next 1-2 hours or so, including: 1)
   continued cooling aloft with approach of a mid-level wave over New
   Mexico and 2) convective organization, which may overcome the cap
   especially in instances of strong updraft rotation and/or upscale
   convective growth.  A few of the operational CAMS indicate this
   potential as well.  This region will also be monitored for a
   potential watch.

   ..Cook/Edwards.. 04/13/2019