DAY 3 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0508 AM CDT TUE MAY 11 2004 VALID 131200Z - 141200Z ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE SOUTHERN AND CENTRAL PLAINS... LARGE UPPER TROUGH WILL MOVE FROM THE ROCKIES INTO THE NORTHERN/CENTRAL PLAINS ON THURSDAY...WITH A SOUTHERN STREAM TROUGH MOVING INTO OK/TX. ALTHOUGH ETA/GFS MODELS AGREE ON GENERAL EVOLUTION OF UPPER FEATURES...CONSIDERABLE DIFFERENCES EXIST REGARDING POSITIONS OF SURFACE BOUNDARIES AND CONVECTIVE CLUSTERS. PREFER THE 00Z ETA SOLUTION...WITH THE SURFACE LOW OVER CENTRAL OK BY AFTERNOON AND DRYLINE EXTENDING SOUTHWARD INTO NORTHWEST TX. RICH GULF MOISTURE SHOULD BE IN PLACE BY THIS TIME AS UPPER 60S TO LOWER 70S SURFACE DEWPOINTS SPREAD ACROSS MUCH OF TX AND OK. THIS COUPLED WITH STRONG DAYTIME HEATING AND STEEP LAPSE RATES WILL LEAD TO AN EXTREMELY UNSTABLE AIRMASS /MLCAPE VALUES AOA 4000 J/KG/. SCATTERED SEVERE/SUPERCELL THUNDERSTORM DEVELOPMENT APPEARS LIKELY ALONG FRONT AND DRYLINE OVER THIS REGION. PRIMARY UNCERTAINTIES IN THIS FORECAST INVOLVE DAY2 CONVECTION AND ITS EFFECTS ON THE OUTLOOK AREA. HOWEVER...IT APPEARS THAT A RATHER SIGNIFICANT SEVERE WEATHER EPISODE WILL OCCUR ON THURSDAY IN PARTS OF KS/OK/TX. ..HART.. 05/11/2004