The SPC is forecasting ...severe thunderstorms expected over parts of the central and southern plains.... Please read the latest public statement about this event.
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SPC AC 231940 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0240 PM CDT MON MAR 23 2009 VALID 232000Z - 241200Z ...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTN/EARLY EVE ACROSS PARTS OF N CNTRL/NE OK INTO CNTRL/ERN KS.... ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN INTO TONIGHT ACROSS PARTS OF THE CNTRL/SRN PLAINS AND MID/LWR MO VALLEY.... ...PLAINS/MISSOURI VALLEY... THE EXIT REGION OF THE STRONG POLAR JET STREAK IS ALREADY SHIFTING NORTHEASTWARD ACROSS THE NORTH CENTRAL PLAINS...WITH AN INITIAL IMPULSE PIVOTING AROUND THE EASTERN PERIPHERY OF A CLOSED MID-LEVEL CIRCULATION OVER WEST CENTRAL NEBRASKA. FORCING ASSOCIATED WITH THIS FEATURE HAS CONTRIBUTED TO ONGOING CONVECTIVE DEVELOPMENT ALONG THE DRY LINE...WHICH ARCS SOUTH OF A THE DEEP SURFACE LOW...ACROSS SOUTH CENTRAL NEBRASKA INTO CENTRAL KANSAS AND WESTERN OKLAHOMA. THROUGH THE REMAINDER OF THE AFTERNOON...ALL INDICATIONS CONTINUE TO SUGGEST THAT THE SURFACE LOW WILL SLOWLY DEEPEN AND MIGRATE NORTHEASTWARD THROUGH THE MID MISSOURI VALLEY...WITH A COLD FRONT OVERTAKING THE DRY LINE ACROSS CENTRAL/EASTERN NEBRASKA AND NORTH CENTRAL KANSAS. THE SPEED AT WHICH THIS OCCURS IS STILL SOMEWHAT UNCERTAIN...AND PRIMARILY AFFECTS THE TRANSITION FROM A MORE DISCRETE CONVECTIVE MODE TO A SOLIDIFYING SQUALL LINE. AS THIS OCCURS...THE POTENTIAL FOR DAMAGING WINDS MAY BECOME MOST PROMINENT...IN THE PRESENCE OF A 50-60 KT DEEP LAYER MEAN FLOW FIELD. LOW-LEVEL MOISTURE VALUES ARE LIKELY TO REMAIN SEEMINGLY ONLY MARGINALLY SUPPORTIVE OF TORNADIC POTENTIAL...BUT LARGE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS AND AMBIENT VERTICAL VORTICITY MAY COMPENSATE...PARTICULARLY LATE THIS AFTERNOON/EARLY EVENING AS ACTIVITY CROSSES DEVELOPING WARM FRONT CLOSER TO THE MISSOURI RIVER. FARTHER SOUTH...THE COLD FRONT IS EXPECTED TO BE SLOWER TO OVERTAKE THE DRY LINE NEAR THE KANSAS/OKLAHOMA BORDER AREA...WHERE FORCING FOR DISCRETE STORMS IS EXPECTED TO REMAIN FAVORABLE INTO AND PERHAPS THROUGH MUCH OF THE EVENING HOURS. SOUTHWESTERLY FLOW BENEATH THE STRONG CYCLONIC MID/UPPER JET AXIS IS EXPECTED TO ADVECT SUSTAINED STORMS...LIKELY SUPERCELLS...AWAY FROM THE DRY LINE. BUT...A RELATIVELY NARROW PRE-FRONT/DRY LINE LOW-LEVEL MOIST TONGUE STILL APPEARS LIKELY TO LIMIT THE PRIMARY SEVERE THREAT WITH THIS ACTIVITY TO PARTS OF NORTH CENTRAL/NORTHEAST OKLAHOMA INTO THE I-35 CORRIDOR OF CENTRAL/EASTERN KANSAS. SLIGHTLY HIGHER BOUNDARY LAYER MOISTURE CONTENT ACROSS THIS REGION /MID TO UPPER 50S SURFACE DEW POINTS/ SHOULD BE MORE CONDUCIVE TO THE RISK FOR TORNADOES...AS COMPARED TO AREAS FARTHER NORTH. EVENTUALLY...THE SURFACE COLD FRONT IS EXPECTED TO OVERTAKE THE DRY LINE LATER THIS EVENING/OVERNIGHT...FROM PARTS OF SOUTHEAST KANSAS THROUGH OKLAHOMA INTO NORTHWEST TEXAS. THIS MAY BE ACCOMPANIED BY AN INCREASE IN CONVECTIVE DEVELOPMENT...PERHAPS AIDED BY FORCING ASSOCIATED WITH THE NEXT IMPULSE...EMANATING FROM THE SOUTHERN GREAT BASIN...BEFORE PIVOTING AROUND THE SOUTHERN/ EASTERN PERIPHERY OF THE CLOSED LOW. WHILE THE SEVERE THREAT DIMINISHES WITH THE STORMS SPREADING EAST OF THE MID MISSOURI VALLEY...AS THEY BECOME CUT-OFF FROM THE BETTER GULF RETURN FLOW ...IT IS POSSIBLE THAT STRONG/SEVERE CONVECTION MAY PERSIST A BIT DEEPER INTO THE NIGHT ACROSS THE SOUTH CENTRAL PLAINS...BEFORE BOUNDARY LAYER BASED INSTABILITY WANES. ..KERR.. 03/23/2009 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z