MESOSCALE DISCUSSION 0575
   NWS STORM PREDICTION CENTER NORMAN OK
   0127 PM CDT SUN APR 28 2013
   
   AREAS AFFECTED...BIG BEND AREA NNEWD INTO W-CNTRL TX
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 281827Z - 282000Z
   
   PROBABILITY OF WATCH ISSUANCE...5 PERCENT
   
   SUMMARY...HIGH BASED THUNDERSTORM CLUSTERS ARE FORECAST TO DEVELOP
   THIS AFTERNOON FROM THE BIG BEND AREA NNEWD INTO W-CNTRL TX.
   ISOLATED STRONG/SEVERE DOWNBURSTS WILL BE POSSIBLE. THREAT IS
   EXPECTED TO BE TOO MARGINAL FOR A WW.
   
   DISCUSSION...TRENDS IN SURFACE OBSERVATIONS SHOW DEWPOINTS HAVE
   RISEN INTO THE 50S ACROSS W TX DUE TO A COMBINATION OF SLY RETURN
   FLOW W OF A SURFACE HIGH CENTERED OVER NERN TX/SWRN AR...AND
   DOWNWARD MIXING OF GREATER MOISTURE LOCATED JUST ABOVE THE SURFACE.
   HOWEVER...AS TEMPERATURES WARM INTO THE MID/UPPER 80S THIS
   AFTERNOON...DEWPOINTS ARE FORECAST TO MIX BACK DOWN INTO THE 30S AND
   40S. DESPITE THE DECREASE IN DEWPOINTS WITH TIME...MLCAPE VALUES
   WILL REMAIN NEAR 500 J/KG DUE TO THE PRESENCE OF VERY STEEP MIDLEVEL
   LAPSE RATES. LOW-LEVEL FOCUS FOR THUNDERSTORM INITIATION IS NOT
   CLEAR ATTM...WITH THE EXCEPTION OF OROGRAPHIC FORCING FOR ASCENT
   OVER THE MOUNTAINOUS TERRAIN IN THE TX TRANS-PECOS.
   NEVERTHELESS...STRONG BOUNDARY LAYER DESTABILIZATION IS STARTING TO
   AID IN DEEPENING CUMULUS DEVELOPMENT...AND HI-RES MODEL GUIDANCE
   INDICATES THIS WILL LEAD TO A FEW HIGH BASED THUNDERSTORM CLUSTERS
   THIS AFTERNOON. DEEPLY MIXED BOUNDARY LAYER PROFILES WILL SUPPORT
   ISOLATED DAMAGING DOWNBURST WINDS.
   
   ..GARNER/HART.. 04/28/2013
   
   
   ATTN...WFO...SJT...LUB...MAF...
   
   LAT...LON   33300259 34110154 33800017 32589984 29740259 29180296
               29110352 29620447 30100464 31570303 33300259