Posted by JAC on 4/17/2009, 8:59 am

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