SPC AC 281959 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK ISSUED BY AFWA OFFUTT AIR FORCE BASE BELLEVUE NE 0259 PM CDT WED MAR 28 2007 VALID 282000Z - 291200Z ...THERE IS A MDT RISK OF SVR TSTMS FROM WRN NEBRASKA...THROUGH WRN KANSAS...WRN OKLAHOMA...AND NW TEXAS... ...THERE IS A SLGT RISK OF SVR TSTMS FROM SD INTO SW TX... ...THERE IS A SLGT RISK OF SVR TSTMS FROM SRN VA INTO NC/NRN SC... ...WIDESPREAD SEVERE THUNDERSTORMS INCLUDING DAMAGING WINDS...VERY LARGE HAIL AND POSSIBLY STRONG TORNADOES WILL DEVELOP OVER THE WESTERN HALF OF THE CENTRAL AND SOUTHERN PLAINS LATER TODAY AND TONIGHT... ...CENTRAL/SRN PLAINS... STRONG UPPER LOW WILL SHIFT INTO THE CENTRAL ROCKIES AND THEN BECOME STATIONARY OVERNIGHT. THE ASSOCIATED SURFACE DRY LINE EXTENDS FROM A LOW OVER FAR NERN CO SWD ALONG THE KS/CO AND TX/NM BORDERS. WIDESPREAD THUNDERSTORM DEVELOPMENT JUST EAST OF THE DRY LINE IS EXPECTED IN THE NEXT FEW HOURS AS THE CAP WEAKENS...WITH SUPERCELLS AND SEVERE WEATHER LIKELY. MLCAPE WILL RANGE FROM 1500-2500 J/KG ACROSS THE AREA...WHILE LOW LEVEL AND DEEP LAYER SHEAR WILL BE STRONG ALONG THE DRY LINE DESPITE STRONGEST MID LEVEL JET EXTENDING NNEWD BEHIND THE DRY LINE OVER CO. HOW LONG ACTIVITY REMAINS IN THE FORM OF DISCRETE SUPERCELLS REMAINS HARD TO SAY...AS ACTIVITY WILL LIKELY EVOLVE INTO LINEAR STRUCTURES AS IT MOVES ENEWD THROUGH THE EVENING. HOWEVER...VERY STEEP LAPSE RATES AND STRONG SHEAR WILL ENHANCE THE POTENTIAL FOR SIGNIFICANT/DAMAGING HAIL AND STRONG TORNADOES INTO THE EARLY-MID EVENING WITH ANY DISCRETE STORMS. WIND DAMAGE THREAT SHOULD ALSO INCREASE AS LINEAR ORGANIZATION BECOMES MORE PREDOMINANT THIS EVENING...BUT THIS WILL BE TEMPERED BY SLOW FORWARD MOTION OF THE CONVECTION DUE TO LINE PARALLEL FLOW. LACK OF EWD PROGRESSION WITH OVERALL SYSTEM AND NARROW INSTABILITY AXIS SUGGESTS STORMS SHOULD WEAKEN AS THEY MOVE ACROSS CENTRAL SD/NE/KS/OK LATER THIS EVENING. NAM AND GFS ARE ALSO INDICATING SECONDARY LOBE OF ENERGY ROTATING AROUND LARGE UPPER LOW AND INTO NERN NM/SERN CO LATE TONIGHT. THIS SHOULD SUPPORT DEVELOPMENT OF ANOTHER MCS...POSSIBLY SEVERE...OVER WRN TX INTO WRN OK/SWRN KS OVERNIGHT. ...SW SD/NW NE... RUC SOUNDINGS INDICATE AROUND 500-1000 J/KG OF SBCAPE ALONG WITH 150-250 J/KG EFFECTIVE HELICITY AND 60-80 KNOTS OF DEEP LAYER SHEAR IN PLACE ACROSS THIS AREA. CONVECTION IS CURRENTLY DEVELOPING IN THE NEBRASKA PANHANDLE AND SUPERCELLS WITH LARGE HAIL AND A FEW TORNADOES ARE POSSIBLE UNTIL AFTER SUNSET WHEN INSTABILITY WILL DIMINISH. ...CENTRAL APPALACHIANS INTO NC... DIFFUSE FRONTAL BOUNDARY IS FOCUSING CONVECTIVE DEVELOPMENT FROM SOUTHERN VIRGINIA INTO NORTHERN NORTH CAROLINA WHERE MLCAPES ARE AROUND 1000 J/KG. 25-30 KNOTS OF MID LEVEL FLOW WILL PROVIDE ENOUGH SHEAR FOR MULTICELLULAR CONVECTIVE MODES WITH LARGE HAIL AND DAMAGING DOWNBURST WINDS POSSIBLE IN THE STRONGER STORMS. ..AFWA.. 03/28/2007 CLICK TO GET WUUS01 PTSDY1 PRODUCT