MESOSCALE DISCUSSION 2152
   NWS STORM PREDICTION CENTER NORMAN OK
   0132 PM CST WED NOV 21 2007
   
   AREAS AFFECTED...E TX...WCNTRL/NWRN LA
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 211932Z - 212130Z
   
   19Z MESOANALYSIS PLACES A PRE-FRONTAL TROUGH EXTENDING FROM NEAR
   KSHV SWWD TO KCLL THEN INTO SCNTRL TX NEAR KSAT.  SSWLY LOW-LEVEL
   FLOW WAS IMPINGING ON THIS BOUNDARY...MAXIMIZING LOW-LEVEL
   CONVERGENCE PRIMARILY NE OF KCLL.  AT THE SAME TIME...WATER VAPOR
   IMAGERY DEPICTED THE LEADING EDGE OF STRONGER LARGE SCALE ASCENT
   MOVING ACROSS SCNTRL TX...DEEPENING THE CIRCULATION VCNTY THE TROUGH
   AND CONTRIBUTING TO TSTM DEVELOPMENT.  
   
   DOWNSTREAM AIR MASS HAD BECOME MODERATELY UNSTABLE WITH MLCAPES OF
   1500-2000 J/KG OWING TO PERSISTENT MOISTURE ADVECTION AND STRONG
   HEATING.  THIS WILL SUPPORT A CONTINUED STRONG TSTM THREAT. 
   VERTICAL SHEAR...HOWEVER...IS COMPARATIVELY WEAKER THAN AT POINTS
   FARTHER EAST AND NORTH.  PAT/LDB PROFILERS SUGGEST THAT DEEP LAYER
   SHEAR THROUGH ABOUT 6 KM IS LESS THAN 25 KTS ATTM.  SOME IMPROVEMENT
   IN THE SHEAR MAY OCCUR LATER THIS AFTN/EVE TO SUPPORT  BRIEF
   SUPERCELL STRUCTURES...BUT IT APPEARS STORMS WILL HAVE A TOUGH TIME
   REMAINING ORGANIZED AS THEY MOVE ESEWD INTO LA AND THE UPR TX. 
   GIVEN IMPROVING MID-LVL LAPSE RATES...MORE ROBUST STORMS MAY PRODUCE
   HAIL ALONG WITH THE THREAT FOR ISOLD DMGG WIND GUSTS THROUGH EARLY
   THIS EVENING.
   
   ..RACY.. 11/21/2007
   
   
   ATTN...WFO...LCH...SHV...HGX...
   
   30539637 31069565 32479423 32929369 32939226 30669294
   29889558 29679640