MESOSCALE DISCUSSION 0267
   NWS STORM PREDICTION CENTER NORMAN OK
   0532 PM CDT SUN APR 04 2004
   
   AREAS AFFECTED...SOUTHERN TX
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 41...
   
   VALID 042232Z - 050030Z
   
   CONTINUE REMAINING VALID PORTION OF WW.  TRENDS ARE BEING MONITORED
   FOR POSSIBILITY OF ADDITIONAL WW.
   
   WITH CLOSED LOW STILL CUT-OFF FROM THE WESTERLIES...UPSTREAM ACROSS
   THE SOUTHERN PLATEAU...LOW-LEVEL CONVERGENCE AND FORCING FOR
   CONVECTIVE DEVELOPMENT IS EXPECTED TO REMAIN FOCUSED ACROSS AREAS
   NEAR/JUST WEST OF THE RIO GRANDE RIVER.  THIS IS WHERE HEATING ALONG
   WESTERN EDGE OF LOW-LEVEL MOIST AXIS WITH UPPER 60S/NEAR 70F DEW
   POINTS HAS CONTRIBUTED TO MEAN MIXED LAYER CAPE IN EXCESS OF 2000
   J/KG.  TENDENCY MAY BE FOR INTENSE NEW CONVECTION...NOW DEVELOPING
   NEAR/WEST OF LAREDO...TO PROPAGATE SOUTH/SOUTHEASTWARD ALONG THE
   HIGHER TERRAIN WEST OF THE RIVER.
   
   HOWEVER...IT APPEARS STRONG CONVECTIVE CLUSTER...NOW TO THE SOUTH OF
   SAN ANTONIO...IS ASSOCIATED WITH WEAK MID-LEVEL CYCLONIC VORTICITY
   CENTER.  THIS FEATURE LIKELY WILL CONTINUE TO DRIFT VERY SLOWLY
   EASTWARD THROUGH UPPER RIDGE AXIS ACROSS THE TEXAS COASTAL PLAIN
   DURING THE EVENING HOURS.  THIS MOTION WILL BE ROUGHLY PARALLEL TO
   WEAK SURFACE BOUNDARY...ALONG WHICH AN AXIS OF STRONGER INSTABILITY
   APPEARS TO EXIST WITH MEAN MIXED LAYER CAPE OF 1000-1500 J/KG.
   
   THUS IT APPEARS SMALL CONVECTIVE SYSTEM WILL PERSIST...WITH A FEW
   VIGOROUS UPDRAFTS CAPABLE OF PRODUCING LARGE HAIL.  DESPITE BEING
   EMBEDDED WITHIN RELATIVELY WEAK FLOW/SHEAR REGIME... POTENTIAL FOR
   GUSTY WINDS APPROACHING SEVERE LIMITS MAY INCREASE AS SURFACE COLD
   POOL STRENGTHENS DURING THE NEXT HOUR OR TWO...IN AREAS SOUTHEAST
   THROUGH EAST NORTHEAST OF SAN ANTONIO. LOCALLY VERY HEAVY RAIN IN
   SLOW MOVING/TRAINING CONVECTION WILL BECOME PRIMARY THREAT THOUGH.
   
   ..KERR.. 04/04/2004
   
   
   ATTN...WFO...HGX...CRP...EWX...BRO...
   
   29939839 30279753 30519664 29999575 29489595 28829738
   28019796 27259872 26880021 28260195 27920084 28229996
   28899881