MESOSCALE DISCUSSION 0495
   NWS STORM PREDICTION CENTER NORMAN OK
   0230 PM CDT WED APR 17 2013
   
   AREAS AFFECTED...PORTIONS OF THE TEXAS SOUTH PLAINS AND SW TX
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 171930Z - 172100Z
   
   PROBABILITY OF WATCH ISSUANCE...60 PERCENT
   
   SUMMARY...SEVERE THREAT IS INCREASING ACROSS THE MCD AREA. STORMS
   ARE EXPECTED BY 21Z BUT COVERAGE MAY REMAIN FAIRLY ISOLATED. STRONG
   WINDS AND LARGE HAIL WILL BE THE MAIN THREAT...BUT A TORNADO IS ALSO
   POSSIBLE.
   
   DISCUSSION...STRONG SURFACE HEATING HAS LEAD TO TEMPERATURES IN THE
   MID 80S TO LOW 90S THIS AFTERNOON IN A MOIST STRONGLY UNSTABLE
   /2500-3000 J PER KG SBCAPE/ AIRMASS EAST OF THE DRYLINE. CURRENT
   MESOANALYSIS INDICATES THAT LITTLE IF ANY SURFACE BASED CINH
   REMAINS...AND THIS IS CONSISTENT WITH FORECAST SOUNDINGS. AGITATED
   CUMULUS HAVE STARTED TO DEVELOP ALONG AND TO THE EAST OF THE DRYLINE
   AND 18Z RAP AND 17Z HRRR GUIDANCE SUGGESTS INITIATION IN THIS AREA
   BY 21Z. EFFECTIVE SHEAR ON THE ORDER OF 40-50 KT AND STEEP LOW TO
   MID LEVEL LAPSE RATES WILL SUPPORT SUPERCELL STRUCTURES CAPABLE OF
   LARGE HAIL AND STRONG WINDS. THE MAGNITUDE OF THE TORNADO THREAT
   APPEARS LESS CLEAR HOWEVER. STRONGER FORCING FOR ASCENT WILL REMAIN
   NORTH OF THE MCD AREA AND STORM COVERAGE MAY REMAIN MORE ISOLATED
   THAN FARTHER TO THE NORTH. THE AREA WILL CONTINUE TO BE MONITORED
   FOR POSSIBLE WW ISSUANCE IN THE NEXT COUPLE OF HOURS.
   
   ..LEITMAN/KERR.. 04/17/2013
   
   
   ATTN...WFO...FWD...OUN...EWX...SJT...LUB...MAF...
   
   LAT...LON   31549861 33079836 33649987 34040070 34090113 33200106
               31880147 31210188 30870154 30520032 30449941 30699898
               31549861