MESOSCALE DISCUSSION 0485
   NWS STORM PREDICTION CENTER NORMAN OK
   0954 PM CDT FRI APR 13 2007
   
   AREAS AFFECTED...TX HILL COUNTRY...LOWER RIO GRANDE VALLEY INTO
   MIDDLE/LOWER TX COAST
   
   CONCERNING...TORNADO WATCH 138...
   
   VALID 140254Z - 140500Z
   
   POTENTIAL FOR MAINLY LARGE HAIL AND LOCALLY DAMAGING WINDS IS
   EXPECTED TO CONTINUE THROUGH 04Z.  THEREAFTER...STORMS MAY TEND TO
   WEAKEN AS THEY APPROACH ERN EDGE OF WW 138.
   
   AS OF 0240Z...SAN ANTONIO RADAR IMAGERY INDICATED A CLUSTER OF
   STRONG TO SEVERE TSTMS OVER HAYS...CALDWELL...COMAL...GUADALUPE AND
   BEXAR COUNTIES...WITH THE SRN MOST STORM EXHIBITING SUPERCELL
   CHARACTERISTICS AS IT MOVES THROUGH THE SAN ANTONIO METRO AREA. 
   INFLOW AIR MASS REMAINS QUITE MOIST WITH DEWPOINTS IN THE LOWER
   70S...EFFECTIVELY CONTRIBUTING TO MLCAPES OF 1000-1500 J/KG.  
   
   00Z SOUNDINGS FROM BRO AND CRP INDICATED THAT BOUNDARY LAYER OVER
   THE MID AND LOWER TX COAST WAS RELATIVELY SHALLOW WITH A
   CONSIDERABLE CAP OBSERVED IN THE 900-700 MB LAYER.  CURRENT THINKING
   IS THAT ONGOING STORMS MAY TEND TO WEAKEN BY 04Z AS THEY CONTINUE
   ESEWD INTO THE PROGRESSIVELY MORE CAPPED AIR MASS.  HOWEVER PRIOR TO
   THIS TIME...STORM-RELATIVE INFLOW OF AROUND 50 KT COUPLED WITH
   NON-HYDROSTATIC PRESSURE GRADIENT FORCE ATTENDANT TO SUPERCELL
   UPDRAFT SHOULD HELP SUSTAIN THE SRN STORM FOR A PERIOD OF TIME AS IT
   ENCOUNTERS A MORE HOSTILE THERMODYNAMIC ENVIRONMENT.
   
   ..MEAD.. 04/14/2007
   
   
   ATTN...WFO...HGX...FWD...CRP...EWX...SJT...
   
   31199833 30889720 30199649 29819647 29259652 28519763
   28489997 28080007 28140038 29290098 30929929