The SPC is forecasting ...a severe thunderstorm outbreak is 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 030557 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1157 PM CST SUN MAR 02 2008 VALID 031200Z - 041200Z ...THERE IS A MDT RISK OF SVR TSTMS ACROSS SERN AR...MUCH OF LA AND MS...AND INTO EXTREME WRN FRINGES OF AL... ...THERE IS A SLGT RISK OF SVR TSTMS FROM E TX ACROSS THE LOWER AND MID MS VALLEY INTO THE TN VALLEY/CENTRAL GULF COAST REGION... ...SYNOPSIS... SIGNIFICANT SEVERE WEATHER EVENT CENTERED INVOF THE LOWER MS VALLEY IS FORECAST THIS PERIOD -- INCLUDING THE POTENTIAL FOR WIDESPREAD/DAMAGING WINDS AND SEVERAL/POTENTIALLY-SIGNIFICANT TORNADOES. LARGE MID-LEVEL TROUGH -- INITIALLY CONSISTING OF A PHASED NRN AND SRN STREAM SYSTEM -- SHOULD EXTEND FROM MN SWWD ACROSS THE CENTRAL PLAINS INTO NM AT THE START OF THE PERIOD. THIS TROUGH IS FORECAST TO SHIFT EWD ACROSS THE PLAINS/UPPER MS VALLEY WITH TIME THROUGH THE FIRST HALF OF THE PERIOD. DURING THE SECOND HALF OF THE PERIOD...THE NRN STREAM FEATURE IS FORECAST TO ACCELERATE EWD ACROSS THE GREAT LAKES AND EVENTUALLY INTO QUEBEC...WHILE THE SRN STREAM FEATURE EVOLVES INTO A CLOSED LOW -- FORECAST TO MOVE INTO AR BY 04/12Z. THE SRN STREAM FEATURE WILL BE ACCOMPANIED BY A VERY STRONG/INTENSIFYING DEEP-LAYER WIND FIELD...INCLUDING A 100-PLUS KT SSWLY H5 JET STREAK. AT THE SURFACE...COLD FRONT WILL SWEEP ACROSS THE MIDWEST AND INTO THE NORTHEAST...WHILE A SURFACE LOW DEVELOPS ON THE TRAILING PORTION OF THIS FRONT AS THE SRN STREAM FEATURE ALOFT STRENGTHENS. THIS LOW -- FORECAST INVOF SRN AR/NRN LA/W CENTRAL MS AT 04/00Z -- IS EXPECTED TO MOVE NEWD INTO MIDDLE TN BY THE END OF THE PERIOD AS COLD FRONT SWEEPS ACROSS THE LOWER MS VALLEY AND INTO THE CENTRAL GULF COAST REGION. ...E TX EWD ACROSS THE LOWER AND MID MS VALLEY INTO SRN KY/TN/NWRN GA/AL/WRN AND CENTRAL FL PANHANDLE... STORMS SHOULD BE ONGOING ALONG/AHEAD OF THE ADVANCING COLD FRONT AT THE START OF THE PERIOD -- FROM SERN MO/AR SWWD ACROSS NERN AND INTO CENTRAL TX. AS SRN STREAM UPPER FEATURE STRENGTHENS...SURFACE LOW SHOULD DEVELOP/MOVE NEWD ALONG THE FRONT ACROSS E TX...ALLOWING THE FRONT TO MOVE QUICKLY SEWD ACROSS TX. BY EARLY AFTERNOON...SLY FLOW WITHIN THE WARM SECTOR FLOW ADVECTING LOW-LEVEL MOISTURE NWD...ALONG WITH SOME HEATING...WILL RESULT IN MODEST DESTABILIZATION /AOB 1000 J/KG/...LIMITED BY WEAK LAPSE RATES ALOFT. DESPITE THIS...VERY STRONG DEEP-LAYER WIND FIELD -- EXPECTED TO VEER SUBSTANTIALLY AND INCREASE RAPIDLY WITH HEIGHT -- WILL RESULT IN DEEP-LAYER SHEAR VERY FAVORABLE FOR SEVERE STORMS...AND LOW-LEVEL SHEAR HIGHLY-SUPPORTIVE OF TORNADOES. THUS...EXPECT SEVERE THREAT TO INCREASE THROUGH THE LATE MORNING INTO THE AFTERNOON. BY MID AFTERNOON...A WELL-DEFINED LINE OF STORMS SHOULD BE MOVING TOWARD THE LOWER MS RIVER...WITH AT LEAST SOME POTENTIAL FOR ISOLATED STORMS DEVELOPING AHEAD OF THE MAIN CONVECTIVE LINE. WHILE LIMITED DEGREE OF INSTABILITY RAISES SOME QUESTION AS TO THE EXTENT OF ISOLATED/PRE-FRONTAL CELLULAR DEVELOPMENT...ATTM IT APPEARS THAT THE POTENTIAL IS GREAT ENOUGH TO SUGGEST THE POSSIBILITY OF MULTIPLE/POTENTIALLY-DAMAGING TORNADOES. TORNADOES WILL ALSO BE POSSIBLE WITHIN THE MAIN CONVECTIVE LINE...THOUGH THE PRIMARY THREAT WITH THIS LINE WILL LIKELY BE WIDESPREAD/POSSIBLY SIGNIFICANT WIND DAMAGE. AFTER DARK...A SLOW DECREASE IN INSTABILITY IS EXPECTED...BUT VERY STRONG/VEERING WIND FIELD WILL LIKELY CONTINUE TO SUPPORT A THREAT FOR DAMAGING WINDS AND TORNADOES. CONVECTION SHOULD SHIFT ACROSS MS AND WRN PORTIONS OF TN AND KY DURING THE EVENING...AND THEN SPREAD ACROSS THE REMAINDER OF KY...TN...AL...AND INTO THE FL PANHANDLE THROUGH THE END OF THE PERIOD. WHILE THE SEVERE THREAT SHOULD SLOWLY DECREASE INTO THE EARLY MORNING...SOME SEVERE POTENTIAL IS EXPECTED TO PERSIST THROUGH THE END OF THE PERIOD. ..GOSS.. 03/03/2008 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z