MESOSCALE DISCUSSION 0447
   NWS STORM PREDICTION CENTER NORMAN OK
   0909 PM CDT SAT APR 11 2009
   
   AREAS AFFECTED...PARTS OF SW...W CNTRL TX
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 139...140...
   
   VALID 120209Z - 120345Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
   139...140...CONTINUES.
   
   REMNANT LOW-LEVEL THERMAL RIDGE OVER THE PECOS VALLEY REMAINS A
   FOCUS FOR BOUNDARY LAYER BASED CONVECTIVE DEVELOPMENT.  MIXED LAYER
   CAPE IS NOT PARTICULARLY STRONG...ON THE ORDER OF 500 J/KG...BUT
   SUFFICIENT IN THE PRESENCE OF STRONG LOW-LEVEL AND DEEP LAYER SHEAR
   FOR SUPERCELLS.  40-50 KT SOUTHWESTERLY DEEP LAYER MEAN FLOW WILL
   SUPPORT ADVECTION OF STORMS TOWARD THE SAN ANGELO/ABILENE AREA...BUT
   THE NEAR SURFACE ENVIRONMENT ACROSS MUCH OF WEST CENTRAL TEXAS WILL
   REMAIN STABLE...AND STORMS LIKELY WILL BECOME ROOTED WITHIN A
   BROADER ELEVATED WARM ADVECTION REGIME. 
   
   NEW STORM DEVELOPMENT OVER THE PECOS VALLEY REGION WILL PROBABLY
   BEGIN TO DIMINISH BY 03-04Z...AS THE LEADING EDGE OF MID-LEVEL
   COOLING SPREADS EASTWARD TOWARD CENTRAL TEXAS...AND THE BOUNDARY
   LAYER ACROSS THE HIGH PLAINS CONTINUES TO COOL.  IT IS POSSIBLE THAT
   AN INCREASINGLY MOIST ELEVATED RETURN FLOW...TO THE NORTH OF A
   LINGERING SURFACE FRONT ACROSS DEEP SOUTH TEXAS...COULD CONTRIBUTE
   TO DESTABILIZATION ACROSS AREAS NEAR AND EAST THROUGH SOUTH OF SAN
   ANGELO TOWARD 06Z.  AS THIS OCCURS...A REINVIGORATION OF CONVECTIVE
   DEVELOPMENT IS POSSIBLE...ACCOMPANIED BY THE RISK FOR LARGE HAIL. 
   BUT...WITH TIME...HEAVY RAIN MAY BECOME THE MORE PROMINENT THREAT IN
   BROAD ZONE OF ISENTROPIC ASCENT FROM PARTS OF THE EDWARDS PLATEAU
   NORTHWARD THROUGH WESTERN/CENTRAL OKLAHOMA.
   
   ..KERR.. 04/12/2009
   
   
   ATTN...WFO...FWD...OUN...SJT...LUB...MAF...
   
   LAT...LON   31350230 32540090 33649997 34039946 34269893 34039830
               33599783 32279848 31079953 30380075 30690192 31350230