The SPC is forecasting ...severe thunderstorms expected over parts of the lower mississippi...lower tennessee...and lower ohio valleys later today into tonight.... Please read the latest public statement about this event.
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SPC AC 240545 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1145 PM CST WED FEB 23 2011 VALID 241200Z - 251200Z ...THERE IS A MDT RISK OF SVR TSTMS OVER CNTRL AND ERN AR...WRN TN...SMALL PART OF SERN MO...NRN MS... ...THERE IS A SLGT RISK OF SVR TSTMS ERN PARTS OF THE SRN PLAINS TO THE LWR OH VLY...LWR MS VLY...MID-SOUTH... ...SYNOPSIS... FORMIDABLE MID-LEVEL SHORTWAVE TROUGH CURRENTLY OVER THE DESERT SW IS EXPECTED TO EJECT ENE ACROSS THE CNTRL/SRN PLAINS THIS AFTERNOON AND ACROSS THE LOWER/MID-MS VLY BY TONIGHT. IN THE LOWER LEVELS...A LOW OVER WCNTRL OK EARLY THIS MORNING WILL INTENSIFY AND MIGRATE INTO SRN MO BY LATE AFTERNOON AND TO THE MID-OH VLY BY 12Z/25. TO THE E OF THE LOW...A WARM FRONT WILL ADVANCE NWD TO ALONG THE MO/AR BORDER BY LATE MORNING AND THE OH VLY LATER IN THE DAY. A PRE-FRONTAL TROUGH WILL MOVE EWD FROM E TX/OK EARLY IN THE DAY TO THE MID-SOUTH AND TN VLY BY TONIGHT. ...ERN OK/TX EWD INTO THE MID-SOUTH/TN VLY... STRONG SLY LOW-LEVEL FLOW IN ADVANCE OF THE APPROACHING MID-LEVEL WAVE WILL TRANSPORT LOWER AND MIDDLE 60S SFC DEW POINTS AS FAR N AS ERN OK...NRN AR AND WRN TN/KY AHEAD OF THE ADVANCING PRE-FRONTAL TROUGH TODAY. THIS WILL CONTRIBUTE TO SUFFICIENT INSTABILITY TO SUPPORT A WIDESPREAD TSTM THREAT AS 90-120 METER MID-LEVEL HEIGHT FALLS SPREAD ENE TODAY AND TONIGHT ACROSS THE SRN PLAINS TO THE MID-SOUTH/TN VLY. TSTMS WILL INCREASE IN THE PRE-DAWN HOURS OVER PORTIONS OF WRN OK/NWRN TX NEAR THE SFC LOW AND DRYLINE/TROUGH AS THE LARGE-SCALE ASCENT/STEEP MID-LEVEL LAPSE RATES BEGIN TO IMPACT WRN PERIPHERY OF MOIST PLUME. THE STORMS WILL LIKELY PRODUCE HAIL DURING THE MORNING HOURS OVER CNTRL OK AND NCNTRL TX OWING TO FAVORABLE MID-LEVEL LAPSE RATE ENVIRONMENT. THE MORNING STORMS WILL LIKELY INTENSIFY WITH ADDITIONAL SFC-BASED ACTIVITY SPROUTING DURING THE LATE MORNING/AFTERNOON FROM NERN TX INTO WRN/CNTRL AR ALONG THE PRE-FRONTAL TROUGH. THESE STORMS WILL PROBABLY OFFER THE BEST OPPORTUNITY FOR HIGHER-IMPACT SEVERE THREATS AS THEY MATURE OVER NRN LA...CNTRL/ERN AR...NWRN MS AND WRN TN DURING THE LATE AFTERNOON-MID-EVENING HOURS. SSWLY 850 MB FLOW IN EXCESS OF 55 KTS BENEATH INCREASING SWLY MID-LEVEL FLOW WILL BOOST OVERALL DEEP-LAYER SHEAR FOR SUPERCELLS. DISCRETE STORMS THAT DEVELOP CLOSE TO THE WARM FRONT...LIKELY IN CNTRL/NERN AR AND WRN TN...WILL BE EMBEDDED IN 200-300 M2/S2 0-1KM SRH AND WILL OFFER THE GREATEST OPPORTUNITY FOR STRONG TORNADOES. ACTIVITY SHOULD EVOLVE INTO A QLCS DURING THE MID-EVENING AND MOVE QUICKLY ENE INTO THE TN VLY/DEEP SOUTH OVERNIGHT. THERE WILL REMAIN A THREAT FOR DAMAGING WINDS/HAIL WELL INTO THE NIGHT...ESPECIALLY OVER PARTS OF MIDDLE TN...MS AND WRN AL. GIVEN THAT THE STRONG FORCING WILL EJECT NEWD TOWARD THE OH VLY...ISOLD DMGG WIND GUSTS WILL BE POSSIBLE AS FAR N AS THE OH RVR AS WELL...THOUGH BETTER INSTABILITY WILL BE FARTHER S. ..RACY/COHEN.. 02/24/2011 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z