The SPC is forecasting ...severe thunderstorms expected over parts of the lower mississippi valley this afternoon and tonight.... Please read the latest public statement about this event.
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SPC AC 031950 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0150 PM CST MON MAR 03 2008 VALID 032000Z - 041200Z ...THERE IS A MDT RISK OF SVR TSTMS MUCH OF MS..PORTIONS SWRN AND EXTREME W-CENTRAL AL...ERN LA...EXTREME SERN AR...EXTREME WRN PANHANDLE OF FL.... ...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM EXTREME SE TX TO MID TN THEN SWD ACROSS NRN/ERN AL TO WRN FL PANHANDLE.... ...SYNOPSIS... MOISTURE CHANNEL IMAGERY CONTINUES TO INDICATE DEEPENING OF MID-UPPER LEVEL LOW ACROSS W TX. THIS CYCLONE SHOULD PIVOT EWD ACROSS N TX AND ARKLATEX REGION OVERNIGHT. AS THIS OCCURS...SFC LOW -- ANALYZED AT 19Z INVOF ELD -- IS EXPECTED TO CONTINUE DEEPENING AS IT MOVES NEWD TOWARD WRN TN. ASSOCIATED ISALLOBARIC FORCING ALREADY IS INTENSIFYING PER LATEST SFC ANALYSIS...AND SHOULD RESULT IN STRENGTHENING OF NEAR-SFC WINDS ACROSS MUCH OF OUTLOOK AREA. ...MS DELTA REGION TO TN VALLEY AND WRN FL PANHANDLE... REF WW 91 AND RELATED MESOSCALE DISCUSSIONS FOR NEAR-TERM SVR THREATS W OF MS RIVER AND OVER WRN MS. RELATIVELY MAXIMIZED SVR POTENTIAL STILL APPEARS TO CORRESPOND TO SHEAR PROFILES AND AT LEAST MRGL INSTABILITY. HAIL POTENTIAL IS WEAKER BECAUSE OF LACK OF THERMODYNAMIC SUPPORT ALOFT. AS SFC LOW CONTINUES TO DEEPEN...ASSOCIATED INCREASE IN ISALLOBARIC FORCING SHOULD RESULT IN MORE VIGOROUS NWD MOISTURE ADVECTION/TRANSPORT ACROSS GULF COASTAL PLAIN THROUGH REMAINDER PERIOD...AHEAD OF MAIN CONVECTIVE BAND. BOW/LEWP MESOCIRCULATIONS ARE PROBABLE WITH ASSOCIATED WIND/TORNADO RISK. AHEAD OF FRONT...CURRENT CONVECTIVE TRENDS SUPPORT A COUPLE OF HIGH-RES/EXPERIMENTAL MODEL FCSTS THAT EVOLVE PREFRONTAL TSTM DEVELOPMENT -- NOW UNDERWAY ACROSS CENTRAL LA -- INTO PRIMARY CONVECTIVE BAND OVER MS/AL THIS EVENING. UNTIL MORE PURELY LINEAR STRUCTURE EVOLVES WITH THAT ACTIVITY...ANY RELATIVELY DISCRETE/SFC-BASED TSTMS MAY BECOME SUPERCELLS AND PRODUCE TORNADOES...A FEW POSSIBLY STG...AMIDST VERY STRONG LOW LEVEL SHEAR PROFILES THAT HAVE BEEN SAMPLED WELL BY LCH/POE VWP DATA AND 18Z RAOBS. THERMODYNAMICALLY...OBSERVED AND MODIFIED 17/18Z RAOBS FROM SHV AND LCH RESPECTIVELY INDICATE EFFECTIVE PARCELS HAVE BECOME SFC BASED AT LEAST AS FAR N AS AROUND I-20 PRIOR TO FROPA. THIS TREND SHOULD CONTINUE TRANSLATING EWD THROUGH REMAINDER DAYLIGHT HOURS INTO MS. AFTER DARK...NOCTURNAL STABILIZATION OF BOUNDARY LAYER SHOULD BE OFFSET BY THETAE ADVECTION TO KEEP PARCELS ROOTED AT/NEAR SFC OVER MDT RISK AREA AND PERHAPS SLIGHTLY FARTHER E INTO SRN/CENTRAL AL. SVR THREAT WILL BECOME MORE CONDITIONAL/MRGL WITH INLAND/NWD EXTENT...LARGELY BECAUSE OF TWO FACTORS... 1. MORE PERSISTENT CLOUD COVER ACROSS ERN AR...NRN MS AND WRN TN...LEADING TO LESS INSOLATION AND SFC HEATING IN SUPPORT OF FAVORABLE DESTABILIZATION...AND 2. LESS TIME FOR GULF RETURN FLOW PRIOR TO FROPA...WITH PROGRESSIVELY MORE ANTICYCLONIC...LOW-THETAE TRAJECTORIES EVIDENT ACROSS TN/KY. STILL...OCCASIONAL DAMAGING GUSTS OR QLCS-TYPE TORNADIC SPINUP CANNOT BE RULED OUT OVER NRN MS/AL AND WRN-MID TN PORTION OF CATEGORICAL SLGT RISK...AND LATE TONIGHT ACROSS NRN/ERN AL AND MID-ERN TN. BECAUSE OF WEAK LAPSE RATES ABOVE SFC...ONLY VERY MINOR ADJUSTMENTS TO BOUNDARY LAYER THETAE OVER THESE REGIONS YIELD PRESENCE OF EITHER NO SFC-BASED BUOYANCY OR ENOUGH TO SUPPORT ORGANIZED SVR WIND/TORNADO POTENTIAL. ..EDWARDS.. 03/03/2008 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z