MESOSCALE DISCUSSION 0492
   NWS STORM PREDICTION CENTER NORMAN OK
   0152 PM CDT WED APR 20 2011
   
   AREAS AFFECTED...TX HILL COUNTRY
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 201852Z - 201945Z
   
   ISOLD-WIDELY SCATTERED SEVERE STORMS EXPECTED TO DEVELOP THIS
   AFTERNOON.  CONVECTIVE INITIATION EXPECTED FIRST /AROUND 20Z/ NEAR A
   MESOLOW-TRIPLE POINT INVOF THE WRN PORTION OF THE TX HILL COUNTRY. 
   LARGE TO VERY LARGE HAIL AND DMGG WIND WILL BE THE MAIN THREATS.
   
   18Z SURFACE ANALYSIS PLACES A 1008 MB LOW 35 MI SSW SJT WHERE A N-S
   DRYLINE IS INTERSECTING A STALLED FRONT ELONGATED FROM THE PECOS
   RIVER VALLEY NEWD INTO NERN TX.  THIS IS WHERE WEAK CONVERGENCE IN
   ADDITION TO HEATING ARE LEADING TO THE DEVELOPMENT OF A SWELLING CU
   FIELD NEAR AND ALONG THE AFOREMENTIONED BOUNDARIES.  THE WARM/MOIST
   SECTOR IS HEATING CONSIDERABLY AS TEMPS WARM WELL INTO THE 80-90S
   AMIDST MID-UPPER 60S DEWPOINTS.  THIS IS CONTRIBUTING TO A VERY
   UNSTABLE AIRMASS WITH 3000-4000 J/KG MLCAPE PER OBJECTIVE ANALYSIS. 
   RECENT RUNS OF THE HRRR SEEM TO RESOLVE WEAKENING INHIBITION INVOF
   THE SWELLING CU FIELD...AND SUGGEST CONVECTIVE INITIATION MAY OCCUR
   AROUND 20Z.
   
   ALTHOUGH MID-HIGH LEVEL FLOW IS RATHER MARGINAL...MODEL FORECAST
   SOUNDINGS SHOW STRENGTHENING SELY LOW LEVEL FLOW TOWARDS THE LATE
   AFTERNOON/EVENING HOURS.  THIS WILL ACT TO ENHANCE EFFECTIVE SHEAR
   ON THE ORDER OF 30-40 KTS...SUFFICIENT FOR ORGANIZED STORMS.  GIVEN
   THE MAGNITUDE OF INSTABILITY COUPLED WITH INCREASING DEEP LAYER
   SHEAR...A FEW SUPERCELLS CAPABLE OF LARGE TO VERY LARGE HAIL...DMGG
   WINDS ARE POSSIBLE THIS AFTERNOON INTO THE EARLY EVENING HOURS.
   
   ..SMITH.. 04/20/2011
   
   
   ATTN...WFO...FWD...EWX...SJT...
   
   LAT...LON   30030076 30600101 31310090 32069908 32159735 31919696
               31369680 31019711 29619974 30030076