MESOSCALE DISCUSSION 0496
   NWS STORM PREDICTION CENTER NORMAN OK
   0728 AM CDT FRI APR 17 2009
   
   AREAS AFFECTED...PARTS OF CENTRAL TX SWD INTO THE RIO GRANDE VALLEY
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 171228Z - 171400Z
   
   A SLOW INCREASE IN SEVERE POTENTIAL EXPECTED OVER THE NEXT COUPLE OF
   HOURS COULD REQUIRE WW ISSUANCE.
   
   A BAND OF STORMS/MCS EXTENDING FROM THE HILL COUNTRY SWWD TO NEAR
   DRT CONTINUES MOVING EWD ACROSS CENTRAL TX.  SOME INCREASE IN THIS
   CONVECTION HAS OCCURRED OVER THE PAST HOUR...WITH A FEW
   STRONGER/ROTATING CELLS PERSISTING WITHIN THE LARGER AREA OF
   CONVECTION.
   
   WITH LOW-LEVEL FLOW CONTINUING TO SLOWLY ADVECT BOUNDARY-LAYER
   MOISTURE NWWD...INSTABILITY INCREASES FROM AROUND 500 J/KG OVER THE
   HILL COUNTRY REGION TO 1500 J/KG NEAR THE SRN FRINGE OF THE ONGOING
   CONVECTION.  FURTHER DESTABILIZATION RESULTING FROM THE ONSET OF
   MODEST HEATING OVER THE NEXT COUPLE OF HOURS COMBINED WITH THIS
   INFLUX OF MOISTURE SHOULD SUPPORT AN INCREASE IN CONVECTION THROUGH
   THE MORNING.  WITH SHEAR SUPPORTIVE OF ROTATING CELLS PER AREA
   VAD/PROFILER DATA...SLOWLY-INCREASING SEVERE THREAT ASSOCIATED WITH
   THIS CONVECTIVE SYSTEM MAY WARRANT WW ISSUANCE.
   
   ..GOSS.. 04/17/2009
   
   
   ATTN...WFO...FWD...CRP...EWX...SJT...
   
   LAT...LON   28600008 29050067 29520027 29929972 30779883 31949846
               31489728 31169691 30029706 29279742 28589847 28600008