The SPC is forecasting ...severe thunderstorms expected over parts of the southern plains this afternoon and tonight.... Please read the latest public statement about this event.
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SPC AC 091210 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0710 AM CDT TUE JUN 09 2009 VALID 091300Z - 101200Z ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF SOUTHERN AND EASTERN KANSAS... ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA FROM NERN CO ACROSS KS/MO AND ALONG THE LOWER OH RIVER VALLEY...AND FROM THE MDT RISK AREA SOUTH ACROSS CNTRL OK AND INTO CNTRL AND SRN TX... ...THERE IS A SLGT RISK OF SVR TSTMS IN THE EAST FROM WRN NC TO SERN PA... ...SIGNIFICANT REGIONAL SEVERE WEATHER OUTBREAK EXPECTED OVER PARTS OF KANSAS...OKLAHOMA...AND MISSOURI TODAY INTO TONIGHT... ...SYNOPSIS... LARGE SCALE SPLIT FLOW REGIME IS CHARACTERIZED BY TROUGHING ACROSS THE U.S./CANADIAN BORDER AND SUB-TROPICAL RIDGE AXIS OVER TX AND THE ADJACENT GULF OF MEXICO. IN THE SRN STREAM...A LOW AMPLITUDE SHORT WAVE TROUGH AND 50-60KT MID LEVEL JET STREAK WILL SPREAD NEWD FROM AZ/NM THIS MORNING TO MO BY TONIGHT. DEEP-LAYER ASCENT WITH THIS DISTURBANCE WILL CONTRIBUTE TO SIGNIFICANT SEVERE TSTM DEVELOPMENT ALONG AND NORTH OF A WELL-DEFINED WARM FRONT FROM KS/OK EWD ACROSS MO TO THE MID MS VALLEY THROUGH EARLY WEDNESDAY. THE WARM FRONT ACROSS NRN OK/ERN KS AREA WILL SERVE AS A FOCUS FOR POTENTIALLY LONG-TRACK SUPERCELLS CAPABLE OF PRODUCING A STRONG TORNADO OR TWO LATER TODAY. A NRN STREAM SHORT WAVE TROUGH AND ASSOCIATED SURFACE LOW WILL TRACK INTO QUEBEC CANADA TODAY. COLD FRONT TRAILING THIS LOW WILL PASS ACROSS PORTIONS OF NY/PA WITH RESIDUAL/WEAKENING STATIONARY PORTION OF THIS FRONT REMAINING ALONG THE OH VALLEY. MODEST HEIGHT FALLS ASSOCIATED WITH THE PASSAGE OF THE NRN STREAM TROUGH MAY INDUCE WEAK CYCLOGENESIS ACROSS DELMARVA REGION LATER TODAY. ...NRN OK/SRN-CNTRL KS AND INTO WRN MO... A WARM AND VERY MOIST AIRMASS RESIDES ACROSS THE SOUTHERN PLAINS THIS MORNING ALONG AND SOUTH OF WARM FRONT FROM SOUTHEAST CO TO THE OK/KS BORDER. TSTMS...ROOTED WELL ABOVE THE BOUNDARY LAYER...WERE INCREASING IN COVERAGE ACROSS KS THIS MORNING AS MASS TRANSPORT AND ISENTROPIC LIFT ARE MAXIMIZED ON THE NOSE OF THE LOW LEVEL JET AND ALONG THE EDGE OF STRONG CAPPING INVERSION. CLOUD COVER AND PRECIPITATION WITH THE ELEVATED STORMS SHOULD INHIBIT SIGNIFICANT NWD RETREAT OF THE WARM FRONT AS VERY UNSTABLE TO EXTREMELY UNSTABLE CONDITIONS DEVELOP FROM SRN/CNTRL KS SWD ACROSS OK. FORECAST SOUNDINGS DEPICT SIGNIFICANT CONVECTIVE INHIBITION/CAPPING ACROSS MUCH OF THE WARM SECTOR THROUGH THE DAY. HOWEVER...MAGNITUDE OF INSTABILITY FUELING ELEVATED STORMS FROM KS INTO MO...AND EFFECTIVE SHEAR THIS AREA...SHOULD BE MORE THAN ADEQUATE FOR LARGE HAIL PRODUCTION AS STORMS INCREASE THROUGH LATE MORNING AND INTO THE AFTERNOON. SURFACE-BASED STORM DEVELOPMENT/INITIATION IS ANTICIPATED AS CAP IS BREACHED THROUGH A COMBINATION OF WEAK LARGE SCALE ASCENT AND PERSISTENT LOW LEVEL CONVERGENCE NEAR DRYLINE/TRIPLE-POINT LOW AND WARM FRONT...SOMEWHERE NEAR SRN KS/NRN OK BY LATE AFTERNOON. THIS AREA SHOULD ALSO LIE NEAR THE SWRN/SRN FLANK OF RAIN-COOLED AIRMASS FROM EARLIER CONVECTION...IN A REGION WHERE THERMAL GRADIENT ALONG THE WARM FRONT MAY BE STRENGTHENED AND LOW LEVEL SHEAR WILL BE MAXIMIZED. GIVEN MAGNITUDE OF AVAILABLE INSTABILITY /MLCAPE AROUND 3000 J/KG/ AND ENLARGED HODOGRAPHS RESULTING IN 0-1KM HELICITY VALUES IN THE RANGE OF 200-400 M2/S2...AND RELATIVELY LOW LFC NEAR THE WARM FRONT...POTENTIAL WILL EXIST FOR LONGER-LIVED SUPERCELLS/MESOCYCLONES CAPABLE OF PRODUCING A STRONG TORNADO OR TWO. IT IS TOO EARLY TO PREDICT EXACTLY WHERE GREATEST TORNADO POTENTIAL WILL EVOLVE AS THIS IS DEPENDENT ON DISCRETE STORM INITIATION NEAR THE AFOREMENTIONED SURFACE FEATURES. AT THIS POINT...THE WARM FRONT AND TRIPLE-POINT LOW ARE MOST LIKELY TO BE LOCATED SOMEWHERE NEAR THE OK/KS BORDER...OR PERHAPS IN SRN/SERN KS AT THE TIME SURFACE-BASED STORM INITIATION BETWEEN THE HOURS OF 20-22 UTC. UPSCALE EVOLUTION INTO A SEVERE MCS IS LIKELY INTO THE EVENING FROM NERN OK/ERN KS SPREADING ACROSS MUCH OF CNTRL/NRN MO THROUGH THE NIGHT. LARGE HAIL IS LIKELY WITH DEEP CONVECTION NORTH OF THE WARM FRONT WHILE DAMAGING WINDS AND A POSSIBLE TORNADO OR TWO WILL ACCOMPANY THE STORMS NEARER THE SURFACE BOUNDARY AND CONVECTIVELY ENHANCED FRONTAL WAVE EXPECTED TO TRACK FROM KS/OK INTO CNTRL MO. ...EAST... AIRMASS RECOVERY IS EXPECTED IN THE WAKE OF MORNING STORMS FROM DELMARVA NWD ACROSS ERN PA. INSTABILITY WILL ALSO INCREASE ALONG THE EAST SLOPES/FOOTHILLS OF THE APPALACHIANS FROM CAROLINAS TO VA. BROADLY DIFFLUENT MID/UPPER FLOW AND WEAK HEIGHT FALLS WITH PASSAGE OF UPPER TROUGH TO THE NORTH WILL FURTHER AID STORM DEVELOPMENT WITHIN MARGINALLY SHEARED FLOW. POCKETS OF SLIGHTLY GREATER SHEAR ACROSS THE MID ATLANTIC AND PERHAPS ACROSS THE CAROLINAS WILL CONTRIBUTE TO POTENTIAL FOR MORE ORGANIZED STORMS THESE AREAS. GREATER PERSISTENCE/ORGANIZATION APPEARS MOST LIKELY ALONG LEE-TROUGH AND NEAR COLD FRONT/LEE-TROUGH INTERSECTION AND DEVELOPING WEAK SURFACE LOW FROM PA ACROSS DELMARVA AREA LATER THIS AFTERNOON. A FEW STORMS IN THESE AREAS MAY BRIEFLY ACQUIRE SUPERCELL STRUCTURE WITH HAIL AND HIGH WINDS POSSIBLE. OTHER MULTICELLULAR STORMS COULD PRODUCE SOME WIND/MARGINAL HAIL BEFORE DIMINISHING IN INTENSITY AFTER SUNSET. ...ERN CO/WRN KS... NARROW CORRIDOR OF DESTABILIZATION /MLCAPE 500-800 J/KG/ IS FORECAST TO DEVELOP ALONG/EAST OF THE STALLED FRONT ACROSS ERN CO. UPSLOPE FLOW AND MODEST LARGE SCALE SUPPORT FOR ASCENT SHOULD PROMOTE STORM INITIATION AS WEAK CONVECTIVE INHIBITION IS OVERCOME. RESULTING STORMS WILL DRIFT EAST INTO HELICITY-RICH ENVIRONMENT ALONG AND EAST OF THE SURFACE BOUNDARY. WITH ELY LOW LEVEL FLOW NORTH OF THE SURFACE/LEE LOW AIDING STORM INFLOW AND SOME TORNADO/HAIL POTENTIAL WITH THIS ACTIVITY. ...CNTRL OK SWWD ALONG TX DRYLINE... AN ENSEMBLE OF VARIOUS GUIDANCE SUGGESTS AT LEAST ISOLATED STORM INITIATION WILL BE POSSIBLE ALONG EXTENSIVE TX DRYLINE FROM SPS/ABI AREAS SWWD TO THE RIO GRANDE. WHILE THIS ENTIRE AREA WILL REMAIN CAPPED BY STOUT EML...IT DOES APPEAR THAT LOCAL HEATING AND MIXING ALONG THE GRADUALLY ADVANCING DRYLINE...ALONG WITH VERY WEAK HEIGHT FALLS ON THE LARGE SCALE...WILL CONTRIBUTE TO POTENTIALLY EXPLOSIVE STORM INITIATION...ESPECIALLY IN TX. INTENSE UPDRAFTS/DOWNDRAFTS WILL LEAD TO HAIL AND HIGH WINDS WITH ANY STORMS THAT DEVELOP IN THIS REGIME. THREAT ACROSS CNTRL OK IS CONDITIONAL ON STORM INITIATION WHICH APPEARS LESS LIKELY GIVEN STRENGTH OF THE CAP. THIS AREA LIES BETWEEN BETTER DEVELOPMENT POTENTIAL TO THE NORTH AND STRONGER HEATING ALONG THE DRYLINE TO THE SOUTH. HOWEVER...GIVEN DEGREE OF INSTABILITY AND SHEAR ACROSS THE AREA ANY CONVECTION BREACHING THE CAP WOULD POSE A THREAT OF LARGE HAIL AND PERHAPS EVEN A TORNADO. THUS...CONDITIONAL SLGT RISK PROBABILITIES APPEAR WARRANTED AT THIS TIME. ..CARBIN/HURLBUT.. 06/09/2009 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z