The SPC is forecasting ...severe thunderstorms expected over parts of the southern plains into the mid and lower mississippi valley this afternoon and tonight.... Please read the latest public statement about this event.
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SPC AC 110100 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0700 PM CST TUE FEB 10 2009 VALID 110100Z - 111200Z ...THERE IS A MDT RISK OF SVR TSTMS ACROSS EASTERN OK...NORTH CENTRAL AND NORTHEAST TX...NORTHWEST LA...WESTERN AND CENTRAL AR...AND FAR SOUTHWEST MO... ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK FROM CENTRAL/ERN TX TO KS/MO/SRN IL... ...A SIGNIFICANT SEVERE WEATHER OUTBREAK -- INCLUDING SUPERCELLS WITH STRONG TORNADOES AND SQUALL LINE PRODUCING DAMAGING WINDS -- WILL SPREAD EWD TONIGHT INTO EARLY WEDNESDAY MORNING FOR ERN OK/NE TX...INTO NW LA...WRN/CENTRAL AR AND FAR SW MO... ...SRN/CNTRL PLAINS TO MS VALLEY... EARLY EVENING SURFACE ANALYSIS INDICATED A COLD FRONT PROGRESSING EWD INTO WRN OK AND TOWARD CENTRAL TX. THIS FRONT WILL ACCELERATE EWD THIS FORECAST PERIOD AS STRONGER ASCENT SPREADS ACROSS THE SRN PLAINS...WITH THE FRONT REACHING CENTRAL MO/AR/LA TO THE NWRN GULF BY 12Z WEDNESDAY. MEANWHILE...A DRY LINE EXTENDED SWD FROM A SURFACE LOW IN SRN OK TO THE TX HILL COUNTRY...AND A BOUNDARY EXTENDED EWD THROUGH NRN AR...MARKING THE NRN EXTENT OF DEEPER LOW LEVEL MOISTURE RETURN /SURFACE DEWPOINTS IN THE LOWER 60S/. 00Z JAN/SHV SOUNDINGS INDICATED DEEP MOISTURE IN THE LOW LEVELS WAS ADVECTING NWD THROUGH E TX AND THE LOWER MS VALLEY. THE STRONG UPPER TROUGH...CURRENTLY LOCATED OVER THE SRN HIGH PLAINS...WILL PROGRESS EWD WITH SOME DEEPENING EXPECTED AS IT BEGINS TO TAKE ON A NEGATIVE TILT LATE TONIGHT...REACHING WRN MO TO WRN AR BY 12Z WEDNESDAY. A SURFACE LOW OVER SERN CO AND THE OK LOW WILL CONSOLIDATE INTO A SINGLE LOW OVER CENTRAL/NERN OK BY LATE EVENING...AND DEEPEN AS STRONG FORCING FOR ASCENT /150-200 METER HEIGHT FALLS/ SPREADS ACROSS THE SRN PLAINS. THE SURFACE LOW SHOULD REACH CENTRAL MO BY EARLY WEDNESDAY MORNING. A FAIRLY BROAD SLY LLJ LOCATED ACROSS THE ERN HALF OF OK/TX INTO THE LOWER MS VALLEY WILL STRENGTHEN TO 60-70+ KT THIS PERIOD IN RESPONSE TO THE HEIGHT FALLS...AS A 110-120 KT WSWLY MID LEVEL JET TRANSLATES ACROSS NRN TX INTO AR BY 12Z. THIS WILL FURTHER ENHANCE LOW LEVEL SHEAR/HELICITY WITH EFFECTIVE HELICITY VALUES RANGING FROM 300-600 M2/S2/. THE STRONG LOW LEVEL SHEAR COMBINED WITH 60-70 KT DEEP LAYER SHEAR VECTORS ORIENTED ACROSS THE WARM SECTOR WILL MAINTAIN LIKELIHOOD FOR DISCRETE TORNADIC SUPERCELLS...SOME STRONG TO SIGNIFICANT. STRONG DEEP LAYER FORCING FOR ASCENT SPREADING EWD ACROSS NRN/CENTRAL TX WILL SUPPORT ADDITIONAL TSTM DEVELOPMENT SWD ALONG THE DRY LINE. DISCRETE STORMS WILL REMAIN POSSIBLE... HOWEVER...EVENTUAL EVOLUTION INTO A FAST MOVING SQUALL LINE IS EXPECTED AS THE COLD FRONT SURGES EWD OVERTAKING THE DRY LINE...WITH THE POTENTIAL FOR SIGNIFICANT WIND DAMAGE ACROSS MUCH OF NRN TX/FAR SRN OK INTO WRN AR/NWRN LA. FARTHER N...TSTMS EXTENDING FROM SERN KS TO ALONG THE MO/AR BORDER WILL SPREAD NNEWD OVERNIGHT AS LOW LEVEL MOISTURE/DESTABILIZATION SPREADS NWD AHEAD OF THE DEEPENING SURFACE LOW. ALTHOUGH INSTABILITY WILL TEND TO BE WEAKER WITH NWD EXTENT...STRONG UPPER FORCING/INCREASING DEEP LAYER SHEAR WILL COMPENSATE AND LIKELY SUPPORT ORGANIZED SEVERE STORMS PRODUCING HAIL AND DAMAGING WINDS. STRENGTHENING SLY WINDS WILL ALSO RESULT IN A TORNADO THREAT INTO THIS REGION. ..PETERS.. 02/11/2009 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z