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Mesoscale Discussion 418
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   MESOSCALE DISCUSSION 0418
   NWS STORM PREDICTION CENTER NORMAN OK
   0143 PM CDT WED APR 22 2015

   AREAS AFFECTED...PORTIONS OF S CNTRL TX

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 221843Z - 222015Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...THUNDERSTORM COVERAGE IS EXPECTED TO INCREASE THROUGH THE
   EARLY AFTERNOON WITH MAINLY A SEVERE HAIL AND WIND THREAT.
   CONVECTIVE TRENDS ARE BEING MONITORED FOR A POSSIBLE WATCH.

   DISCUSSION...SUBTLE FORCING FOR ASCENT EMBEDDED WITHIN THE
   SUBTROPICAL JET HAS ENCOURAGED THUNDERSTORM DEVELOPMENT BETWEEN DEL
   RIO AND SAN ANTONIO THE LAST HOUR ON THE EASTERN EDGE OF A CAPPING
   INVERSION. DESPITE ABUNDANT MID-TO-HIGH-LEVEL CLOUDS...SURFACE
   TEMPERATURES IN THE MCD AREA HAVE WARMED INTO THE UPPER 70S TO LOW
   80S F WITHIN A MOIST BOUNDARY LAYER CHARACTERIZED BY UPPER 60S F
   SURFACE DEWPOINTS. EFFECTIVE SHEAR OF 50-60 KT AND MUCAPE VALUES
   CLIMBING INTO THE 1500-2000 J/KG RANGE WILL ENCOURAGE ORGANIZED
   CONVECTIVE STRUCTURES WITH A THREAT FOR SEVERE HAIL AND DAMAGING
   WIND GUSTS. 

   THE DOMINANT CONVECTIVE MODE TO EMERGE IS UNCERTAIN. THE STORMS WEST
   OF SAN ANTONIO ARE CURRENTLY IN A MULTICELL CLUSTER...BUT A
   RELATIVELY DEEP MOIST BOUNDARY LAYER MAY PRECLUDE ORGANIZED COLD
   POOL DEVELOPMENT. THUS A FEW SUPERCELLS ARE EXPECTED TO EMERGE FROM
   THE CLUSTER OR ANY SUBSEQUENT CELLS THAT DEVELOP IN THE MCD AREA.
   REGARDLESS OF THE DOMINANT CONVECTIVE MODE...RELATIVELY WEAK
   LOW-LEVEL WINDS THAT HAVE VEERED TO A SOUTHERLY/SOUTHEASTERLY
   DIRECTION THROUGH MOST OF THE BOUNDARY LAYER PER VAD WIND PROFILES
   SHOULD KEEP TORNADO POTENTIAL LOW OVER THE NEXT FEW HOURS.

   ..CONIGLIO/GLEASON/HART.. 04/22/2015


   ATTN...WFO...HGX...EWX...

   LAT...LON   29169698 29009748 28879808 28749866 28849911 29239942
               29849931 30299833 30469726 30319647 30089627 29599626
               29289643 29169698 

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Page last modified: April 22, 2015
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