MESOSCALE DISCUSSION 0876
   NWS STORM PREDICTION CENTER NORMAN OK
   0823 PM CDT TUE MAY 26 2009
   
   AREAS AFFECTED...PORTIONS S TX.
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 270123Z - 270330Z
   
   CONDITIONAL POTENTIAL EXISTS FOR CONTINUING/NEW SVR DEVELOPMENT OVER
   THIS AREA...WITH UPSCALE GROWTH AND INCREASING COVERAGE OF
   CONVECTION POSSIBLE.  INCREASING CAP WILL BE LIMITING FACTOR.
   
   SMALL CLUSTER OF STG-SVR TSTMS OVER NWRN VAL VERDE COUNTY MAY
   EXPAND...AND IN COMBINATION WITH TSTMS NOW FARTHER SW ACROSS NRN
   COAHUILA...BUILD SUFFICIENTLY STG COLD POOL TO MAINTAIN
   FORWARD-PROPAGATIONAL COMPLEX ESEWD ACROSS SRN EDWARDS PLATEAU/SRN
   HILL COUNTRY REGION AND ADJACENT PORTIONS RIO GRANDE VALLEY. 
   MODIFIED DRT RAOB SUGGESTS DIABATIC SFC COOLING SIGNIFICANTLY
   STRENGTHENS SBCINH IN PROSPECTIVE INFLOW REGION...THROUGH WHICH
   INCREASINGLY STG FORCED ASCENT WILL BE NEEDED TO MAINTAIN BOTH
   SFC-BASED EFFECTIVE PARCELS AND DAMAGING DOWNDRAFT POTENTIAL. 
   MLCAPE 1000-1500 J/KG...AND AROUND 40 KT EFFECTIVE SHEAR
   MAGNITUDE...WILL SUPPORT SVR THREAT AS LONG AS SFC-BASED INFLOW CAN
   BE MAINTAINED.  FARTHER SW...BAND OF CU/TCU HAS BEEN EVIDENT FOR 1-2
   HOURS FROM NWRN WEBB COUNTY EWD TO SEA BREEZE OVER WRN NUECES
   COUNTY...NEAR AND JUST W OF WHERE SFC DATA HAS INDICATED WEAK
   MESOLOW.  ANY SUSTAINED TSTM THAT MAY DEVELOP ALONG THIS CONVERGENCE
   ZONE MAY PRODUCE LARGE HAIL...GIVEN 2000 J/KG MLCAPE AND 40-50 KT
   EFFECTIVE SHEAR DERIVED FROM MODIFIED CRP RAOB.  HOWEVER...THIS VERY
   CONDITIONAL SVR THREAT ALSO WILL BECOME MORE IMPROBABLE AFTER ABOUT
   02Z...WHEN SFC COOLING STRENGTHENS MLCINH APPRECIABLY.
   
   ..EDWARDS.. 05/27/2009
   
   
   ATTN...WFO...CRP...EWX...BRO...SJT...MAF...
   
   LAT...LON   29800194 30270157 30330088 30139986 29629906 28879920
               28289918 28009816 27429772 27329871 27329952 27639957
               27639967 28160013 28240026 28850060 29250079 29380105
               29620125 29570133 29780145 29800194