Posted by JAC on 5/1/2009, 4:00 pm, in reply to "Severe weather for OK/TX this afternoon"

MESOSCALE DISCUSSION 0656 NWS STORM PREDICTION CENTER NORMAN OK 0248 PM CDT FRI MAY 01 2009 AREAS AFFECTED...NWRN TX...SRN OK CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY VALID 011948Z - 012115Z ...TORNADO WATCH WILL LIKELY BE ISSUED BY 21Z FOR PORTIONS OF NWRN TX AND SRN OK... LATEST SFC ANALYSIS INDICATES STRONG BOUNDARY LAYER HEATING HAS ALL BUT REMOVED WHAT LITTLE INHIBITION EXISTED ALONG DRYLINE/COLD FRONT ACROSS NWRN TX. AS A RESULT...CU FIELD IS BEGINNING TO EXPAND/DEEPEN ACROSS THIS REGION...PRIMARILY WHERE SFC TEMPERATURES HAVE WARMED INTO THE LOWER 90S BETWEEN CDS-ABI...JUST SOUTH OF THE SFC FRONT. ALTHOUGH DEEP LAYER SHEAR IS SOMEWHAT MARGINAL...SFC-6KM VALUES ON THE ORDER OF 30KT...INSTABILITY IS BECOMING QUITE IMPRESSIVE AS LAPSE RATES STEEPEN IN EXCESS OF 8 C/KM...YIELDING MLCAPE VALUES ON THE ORDER OF 4500 J/KG. IT APPEARS THUNDERSTORMS WILL EVOLVE IN THE NEXT FEW HOURS ALONG ADVANCING COLD FRONT/DRYLINE WITH SUBSEQUENT SLOW SEWD EXPANSION EXPECTED ACROSS NWRN TX/SRN OK. WITH DEW POINTS NOW WELL INTO THE UPPER 60S IT APPEARS THERMODYNAMIC PROFILES WILL COMPENSATE FOR WEAKER SHEAR AND SUPPORT AT LEAST A RISK FOR TORNADOES WITH SLOW-MOVING HP SUPERCELLS. ..DARROW.. 05/01/2009