The SPC is forecasting ...significant severe thunderstorms expected over the upper ms valley into parts of the mid mo valley later today and tonight.... Please read the latest public statement about this event.
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SPC AC 170548 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1248 AM CDT THU JUN 17 2010 VALID 171200Z - 181200Z ...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS PARTS OF ERN NORTH DAKOTA...WRN/CNTRL AND SRN MINNESOTA...PARTS OF ERN SOUTH DAKOTA...ERN NEBRASKA...IOWA...AND WRN WISCONSIN... ...THERE IS A SLGT RISK OF SVR TSTMS TODAY AND TONIGHT ACROSS PARTS OF THE NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY... ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN AND EVE ACROSS UPPER PORTIONS OF THE LWR MISSISSIPPI VALLEY INTO THE NORTH CENTRAL GULF STATES... ...SYNOPSIS... MODELS INDICATE THAT LARGE-SCALE UPPER TROUGHING WILL LINGER ACROSS THE PACIFIC COAST...INTERMOUNTAIN WEST...AND ROCKIES THROUGH THIS FORECAST PERIOD. BUT A VIGOROUS SHORT WAVE IMPULSE IS IN THE PROCESS OF LIFTING OUT OF THE GREAT BASIN...AND THIS FEATURE IS PROGGED TO PIVOT ACROSS THE NORTHERN PLAINS IN NEGATIVELY TILTED FASHION...TO THE EAST OF A DEVELOPING MID-LEVEL CIRCULATION SHIFTING TOWARD THE CENTRAL CANADIAN/U.S. BORDER. THIS APPEARS LIKELY TO BE ACCOMPANIED BY A DEEP OCCLUDING SURFACE CYCLONE...WITH THE ASSOCIATED COLD FRONT ADVANCING THROUGH MUCH OF THE NORTHERN/CENTRAL PLAINS AND UPPER MISSISSIPPI VALLEY BY 12Z FRIDAY. TO THE SOUTH...SUBTROPICAL RIDGING IS EXPECTED TO PERSIST ACROSS MUCH OF THE SOUTH CENTRAL AND SOUTHEASTERN STATES. HOWEVER...AN EMBEDDED HIGH CENTER APPEARS TO BE SHIFTING FROM THE EASTERN GULF OF MEXICO/FLORIDA PENINSULA REGION INTO THE CENTRAL GULF COAST/ LOWER MISSISSIPPI VALLEY...WHERE IT IS GENERALLY PROGGED TO LINGER THROUGH THE PERIOD. ...NORTHERN PLAINS/UPPER MISSISSIPPI VALLEY... SOME VARIABILITY EXISTS AMONG THE MODELS CONCERNING THE DETAILS OF THE EVOLUTION OF THE FRONTAL OCCLUSION...AND THE PRE-FRONTAL DRY LINE...ACROSS THE EASTERN DAKOTAS AND EASTERN NEBRASKA INTO MINNESOTA AND IOWA TODAY...PERHAPS AT LEAST IN PART DUE TO THE LIKELY PRESENCE OF EARLY DAY CONVECTION. HOWEVER...GENERAL AGREEMENT EXISTS CONCERNING THE DEVELOPMENT OF MODERATE TO STRONG INSTABILITY NEAR/EAST OF THE MID MISSOURI VALLEY INTO THE UPPER MISSISSIPPI VALLEY. BENEATH THE NOSE OF A PLUME OF ELEVATED MIXED LAYER AIR EMANATING FROM THE PLATEAU REGION...WARM SECTOR SURFACE DEW POINTS ARE EXPECTED TO RISE TO AROUND OR ABOVE 70F BY PEAK AFTERNOON HEATING...WHEN MIXED LAYER CAPE OF 2000-3000+ J/KG APPEARS LIKELY. BOUNDARY LAYER BASED STORMS APPEAR MOSTLY LIKELY TO INITIATE AS THE LEADING EDGE OF STRONGER MID-LEVEL COOLING...ASSOCIATED WITH THE UPPER TROUGH...OVERSPREADS THE WARM SECTOR LATE THIS AFTERNOON. A WINDOW OF OPPORTUNITY FOR DISCRETE STORMS SEEMS TO EXIST...WITH VERTICAL SHEAR IN THE VICINITY OF A 50-70 KT WESTERLY 500 MB JET STREAK SUFFICIENT FOR SUPERCELLS CAPABLE OF PRODUCING TORNADOES. 30 TO 50 KT SOUTHERLY 850 MB FLOW WILL RESULT IN SIZABLE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS...BUT A WEAKNESS IN HIGH-LEVEL FLOW...BENEATH DIFLUENT UPPER JET STREAKS ...COULD CONTRIBUTE TO UPSCALE CONVECTIVE GROWTH INTO A LARGE MESOSCALE CONVECTIVE SYSTEM. TORNADIC POTENTIAL WILL LARGELY BE DEPENDENT ON HOW QUICKLY THIS OCCURS. AT THE PRESENT TIME...IT SEEMS THAT THE DAMAGING WIND POTENTIAL MAY BECOME MORE PROMINENT ...ESPECIALLY BY EARLY EVENING ACROSS MINNESOTA AND IOWA. THIS THREAT MAY PERSIST INTO THE OVERNIGHT HOURS...BEFORE WANING WITH EASTWARD AND SOUTHEASTWARD ADVANCEMENT OF THE CONVECTIVE COLD POOL TOWARD THE UPPER GREAT LAKES REGION AND MIDDLE MISSISSIPPI VALLEY. ...LOWER MISSISSIPPI VALLEY/GULF STATES... TYPICAL UNCERTAINTIES EXIST CONCERNING THE SEVERE POTENTIAL WITHIN SEASONABLY WEAK FLOW...BUT MODERATE TO STRONG INSTABILITY IS EXPECTED WITH HEATING OF A CONTINUING MOIST BOUNDARY LAYER. THERE ARE INDICATIONS AMONG THE MODELS THAT A CONVECTIVELY GENERATED OR ENHANCED PERTURBATION COULD ROUND THE NORTHEASTERN PERIPHERY OF THE HIGH CENTER...ACROSS THE OZARKS INTO THE NORTHERN GULF STATES...CONTRIBUTING TO THE EVOLUTION OF ANOTHER CONVECTIVE CLUSTER LATE THIS AFTERNOON OR EVENING. IF THIS OCCURS...A TRANSITION FROM LOCALIZED DOWNBURSTS TO MORE GENERAL GUSTS APPROACHING OR BRIEFLY EXCEEDING SEVERE LIMITS COULD OCCUR ALONG THE LEADING EDGE OF SOUTHEASTWARD ADVANCING AND CONSOLIDATING SURFACE COLD POOLS. ..KERR/HURLBUT.. 06/17/2010 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z