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 101621 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1021 AM CST TUE FEB 10 2009 VALID 101630Z - 111200Z ...THERE IS A MDT RISK OF SVR TSTMS OVER PORTIONS OF CENTRAL/EASTERN OK...NORTH CENTRAL AND NORTHEAST TX...NORTHWEST LA...AND MUCH OF AR... ...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF THE SOUTHERN PLAINS AND LOWER/MID MS VALLEY... ...A SIGNIFICANT SEVERE WEATHER OUTBREAK -- INCLUDING SUPERCELLS WITH STRONG TORNADOES -- IS EXPECTED THIS AFTERNOON INTO TONIGHT FOR ERN OK/NE TX...INTO WRN/CENTRAL AR AND NW LA... MORNING WATER VAPOR SHOWS A VIGOROUS AND DIGGING SHORTWAVE TROUGH OVER EASTERN AZ. THIS FEATURE WILL ROTATE INTO TX THIS EVENING...WHILE 110+ KT MID LEVEL JET NOSES INTO THE BIG BEND REGION. PARAMETERS REMAIN VERY FAVORABLE FOR NUMEROUS SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS THIS AFTERNOON AND TONIGHT WITH A RISK OF WIDESPREAD DAMAGING WINDS...STRONG TORNADOES...AND LARGE HAIL. 15Z SURFACE ANALYSIS SHOWS LOW LEVEL MOISTURE RETURNING RAPIDLY NORTHWARD ACROSS EAST TX INTO OK/AR. BY MID AFTERNOON...IT APPEARS LIKELY THAT THE SURFACE DRYLINE WILL BECOME ESTABLISHED ROUGHLY ALONG A LINE FROM W OF OKC...LAW...ABI. HIGH CLOUDS ARE CLEARING OUT OF THIS REGION...AND LOW CLOUDS WILL SLOWLY ERODE THIS MORNING. THIS WILL ALLOW RELATIVELY STRONG HEATING ALONG THE DRYLINE AND LEAD TO AFTERNOON MLCAPE VALUES AROUND 1000 J/KG. FARTHER EAST...GREATER LOW LEVEL MOISTURE WILL OFFSET MORE CLOUD COVER WITH MLCAPE OF OVER 1000 J/KG EXPECTED. ...DRYLINE INITIATION OK/TX... GIVEN LATEST MODEL GUIDANCE AND OBSERVATIONAL TRENDS... THUNDERSTORMS ARE EXPECTED TO DEVELOP 20-22Z ALONG DRYLINE OVER WESTERN OK AND NORTHWEST TX. THESE STORMS WILL LIKELY BE SUPERCELLULAR WITH A RISK OF VERY LARGE HAIL AND TORNADOES. THE STORMS WILL BECOME MORE NUMEROUS BY EARLY EVENING /AFTER DARK/ AND TRACK NORTHEASTWARD INTO NORTHEAST TX AND EASTERN OK. MUCH STRONGER VERTICAL SHEAR PROFILES IN THIS REGION /EFFECTIVE HELICITY OF 400+ M2/S2/ WILL ALSO INCREASE THE RISK OF STRONG TORNADOES. HAVE CHOSEN TO MAINTAIN CATEGORICAL MODERATE RISK FOR THIS AFTERNOON DUE TO CONTINUED CONCERNS OVER THE QUALITY OF LOW LEVEL MOISTURE...BUT AN UPGRADE TO HIGH RISK WILL REMAIN POSSIBLE AT 20Z. ...MAIN SQUALL LINE TX/EASTERN OK... BY LATE AFTERNOON...THE PRIMARY UPPER FORCING WILL ARRIVE ALONG THE DRYLINE/PACIFIC FRONT OVER NORTHWEST TX. THIS WILL LIKELY RESULT IN THE RAPID DEVELOPMENT OF AN INTENSE SQUALL LINE. THIS ACTIVITY IS EXPECTED TO TRACK EASTWARD ACROSS NORTH-CENTRAL AND CENTRAL TX DURING THE EVENING WITH A RISK OF WIDESPREAD DAMAGING WINDS. LOW AND DEEP LAYER VERTICAL SHEAR PROFILES WILL BE VERY FAVORABLE FOR EMBEDDED MESOCYCLONES AND THE RISK OF TORNADOES. FORECAST SOUNDINGS ALSO SUGGEST ONLY A WEAK CAP AHEAD OF THE SQUALL LINE...POSING THE RISK OF MORE DISCRETE TORNADIC SUPERCELLS DURING THE EVENING. STRONG TORNADOES WILL BE POSSIBLE OVER THIS REGION AS WELL. ...OVERNIGHT LA/AR/MO... WIDESPREAD THUNDERSTORMS WILL ACCELERATE THROUGH THE EVENING AND SWEEP EASTWARD INTO PARTS OF LA/AR/MO OVERNIGHT. THE 500MB JET MAX WILL INCREASE TO OVER 120 KT DURING THIS PERIOD...SUGGESTING A CONTINUED RISK OF WIDESPREAD DAMAGING WINDS AND EMBEDDED TORNADOES THROUGH MUCH OF THE NIGHT. STORMS MAY REACH SOUTHERN IL/WEST TN/NORTHWEST MS BY 11/12Z. ...NORTHERN OK/SOUTHERN KS... MODEL GUIDANCE SUGGESTS THAT PRIMARY SURFACE LOW WILL BECOME ESTABLISHED BY LATE AFTERNOON OVER SOUTHWEST KS...WITH BACKED LOW LEVEL WINDS AND INCREASING MOISTURE INTO PARTS OF NORTHWEST OK/SOUTHERN KS. FULL SUNSHINE WILL LEAD TO STEEP LOW LEVEL LAPSE RATES AND SUFFICIENT INSTABILITY FOR THE DEVELOPMENT OF ISOLATED THUNDERSTORMS BY EARLY EVENING. VERTICAL SHEAR PROFILES ARE WEAKER IN THIS REGION THAN FARTHER SOUTHEAST. HOWEVER... PARAMETERS SUGGEST THE RISK OF A FEW SUPERCELLS CAPABLE OF LARGE HAIL AND ISOLATED TORNADOES. ..HART.. 02/10/2009 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z