MESOSCALE DISCUSSION 0504
   NWS STORM PREDICTION CENTER NORMAN OK
   0219 PM CDT THU APR 21 2011
   
   AREAS AFFECTED...TX PECOS RIVER VALLEY
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 211919Z - 212015Z
   
   STORM INITIATION IS EXPECTED WITHIN THE NEXT HOUR OR SO ACROSS THE
   TX PECOS RIVER VALLEY.  SUPERCELLS CAPABLE OF LARGE TO VERY LARGE
   HAIL AND DMGG WINDS WILL BE THE PRIMARY HAZARDS.  A WW MAY BE
   REQUIRED TO ADDRESS THIS THREAT AND THE 20Z CONVECTIVE OUTLOOK
   UPDATE WILL INCLUDE THIS AREA IN A SLIGHT RISK.
   
   WATER VAPOR TRENDS THE PAST FEW HOURS SHOWS A WEAK IMPULSE MOVING
   ACROSS ERN NM AND PARTS OF W TX.  THIS IS EVIDENT IN WSM PROFILER
   TIME SERIES WITH FLOW INCREASING BY 20 KTS IN THE MID-UPPER LEVELS
   SINCE THIS MORNING.  ASCENT ASSOCIATED WITH THIS FEATURE...IMPLIED
   BY EWD MOVING BROKEN CIRRUS SHIELD...IS NOW SPREADING TOWARDS THE S
   PLAINS AND THE LOWER PECOS RIVER VALLEY.  LATEST SURFACE ANALYSIS
   SHOWS 1MB/HR SURFACE PRESSURE FALLS THE PAST FEW HOURS SEEMINGLY
   REFLECTIVE OF THE UPPER FEATURE WITH RICH LOW LEVEL MOISTURE
   CHARACTERIZED BY MID 60S DEWPOINTS HOLDING ACROSS THE LOWER PECOS
   RIVER VALLEY IN SWRN TX.  STRONG HEATING ACROSS THE
   REGION...PREFERABLY FAVORING HIGHER TERRAIN/ HAS ESSENTIALLY
   WEAKENED THE REMAINING CAP.  AS SUCH...EXPECTING STORM INITIATION BY
   20Z NEAR THE GLASS MTNS AND FST.  
   
   VERY STEEP LAPSE RATE ENVIRONMENT ATOP THE AFOREMENTIONED MOIST
   BOUNDARY LAYER HAS LED TO A VERY UNSTABLE AIRMASS /3500 J/KG MLCAPE
   PER OBJECTIVE ANALYSIS/.  MOIST SELY UPSLOPE FLOW UNDERNEATH
   INCREASING DEEP LAYER SHEAR WILL BE SUPPORTIVE OF A SUPERCELL WIND
   PROFILE AND RESULT IN STORMS RAPIDLY DEVELOPING AND BEING CAPABLE OF
   LARGE TO VERY LARGE HAIL AND DMGG WINDS ONCE SUPERCELL STRUCTURE IS
   ATTAINED.  ALTHOUGH ONLY ISOLD STORM COVERAGE IS EXPECTED...THE
   NATURE OF THE THREAT MAY WARRANT A WW ISSUANCE WITHIN THE NEXT HOUR
   OR TWO.
   
   ..SMITH.. 04/21/2011
   
   
   ATTN...WFO...EWX...SJT...LUB...MAF...
   
   LAT...LON   29900301 30730358 31250312 33060072 33070003 32419974
               30030036 29490042 28970088 29060246 29900301