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Mesoscale Discussion 439
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   MESOSCALE DISCUSSION 0439
   NWS STORM PREDICTION CENTER NORMAN OK
   0456 PM CDT FRI APR 24 2015

   AREAS AFFECTED...S TX

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 242156Z - 242330Z

   PROBABILITY OF WATCH ISSUANCE...60 PERCENT

   SUMMARY...TSTMS DEVELOPING OVER THE HIGHER TERRAIN OF NERN MX WILL
   APPROACH THE RIO GRANDE VALLEY WITHIN THE NEXT HR. PARTS OF S TX ARE
   BEING MONITORED FOR A POSSIBLE WW.

   DISCUSSION...TSTMS DEVELOPING NEAR THE HIGHER TERRAIN OF NERN MX ARE
   EXPECTED TO REACH THE RIO GRANDE VALLEY /S OF DRT/ BY 23Z. STRONG
   HEATING WITHIN A MOISTURE-RICH AIR MASS IS YIELDING MLCAPE VALUES OF
   2500-3500 J/KG...AND A WEAKENING CAP WHERE TEMPERATURES HAVE WARMED
   INTO THE MID-UPPER 80S F. 50 KT MIDLEVEL SWLYS ARE SUFFICIENT FOR
   ORGANIZED STORMS...WITH AN ACCOMPANYING THREAT FOR LARGE HAIL AND
   DMGG WIND GUSTS. LOW-LEVEL FLOW IS WEAK...BUT VEERS WITH HEIGHT...SO
   A TORNADO THREAT CANNOT BE RULED OUT GIVEN THE MAGNITUDE OF
   INSTABILITY AND STEEP LOW-LEVEL LAPSE RATES.

   THE MOST FAVORABLE ZONE FOR SVR TSTMS IN THE SHORT-TERM WILL BE
   DOWNSTREAM FROM DEVELOPING CONVECTION /ROUGHLY BETWEEN DRT AND LRD
   AND AREAS TO THE E/. ADDITIONAL WEAKER CONVECTION WAS DEVELOPING
   FARTHER S UPSTREAM FROM ZAPATA/WEBB COUNTIES...BUT WILL LIKELY BE AT
   LEAST 2 HRS BEFORE THESE AREAS ARE AFFECTED. SPATIAL COVERAGE OF
   TSTMS THROUGH THE EARLY EVENING IS SOMEWHAT UNCERTAIN GIVEN
   OROGRAPHIC FORCING BEING PRIMARY FOCUS FOR ASCENT. HOWEVER...TRENDS
   CONTINUE TO BE MONITORED FOR POSSIBLE WW ISSUANCE.

   ..ROGERS/DIAL/THOMPSON.. 04/24/2015


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

   LAT...LON   29520118 29730078 29769944 29469862 28559828 26159834
               26269873 26439907 26899936 27069944 27559949 27729979
               28340033 28930063 29150077 29520118 

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Page last modified: April 24, 2015
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