SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0100 AM CDT WED MAY 02 2012 VALID 021200Z - 031200Z ...THERE IS A MDT RISK OF SVR TSTMS FROM CNTRL NEB INTO CNTRL IA... ...THERE IS A SLGT RISK OF SVR TSTMS FROM NEB AND SD EWD ACROSS LOWER MI AND INTO THE DELMARVA... ...SYNOPSIS... A BROAD BELT OF SWLY FLOW ALOFT WILL EXTEND FROM THE NRN ROCKIES ACROSS THE NRN PLAINS AND UPPER MS VALLEY. ONE LEAD SHORTWAVE WILL EXIST OVER THE UPPER MS VALLEY AT 12Z WED...AND WILL QUICKLY MOVE NEWD ACROSS THE GREAT LAKES AND INTO ONTARIO. BEHIND THIS WAVE...HEIGHT MAY RISE BRIEFLY AHEAD OF THE NEXT SHORTWAVE TROUGH WHICH WILL AFFECT WRN NEB AND THE DAKOTAS BY 00Z. A LOW LEVEL JET WILL ALSO INCREASE DURING THE EVENING OVER THIS REGION...HELPING TO FUEL COMPLEXES OF SEVERE THUNDERSTORMS FROM NEB INTO IA. ANOTHER WEAK SHORTWAVE WILL EXIST FROM OH INTO THE MID ATLANTIC AND WILL ENHANCE STORM CHANCES THERE. AT THE SURFACE...A VERY LARGE AREA OF MOISTURE AND INSTABILITY WILL BE PRESENT ACROSS THE PLAINS AND MIDWEST EWD ACROSS THE OH/TN VALLEYS AND TO THE MID ATLANTIC. AS A RESULT...A VERY ACTIVE CONVECTIVE DAY IS ANTICIPATED. ...NRN IA/SRN MN...SRN WI AND NRN IL AFTERNOON... AN MCS ONGOING THIS EVENING WILL LIKELY LEAVE BEHIND A SLIGHTLY COOLER AIR MASS OVER PORTION OF IA...MN...AND WI...REINFORCING THE SYNOPTIC BOUNDARY. STRONG INSTABILITY AND A SWLY LOW LEVEL JET MAY ALLOW FOR A CONTINUATION OF SOME ACTIVITY EARLY...FROM NRN MO INTO ERN IA AND NRN IL WITH A MARGINAL THREAT OF WIND AND HAIL. DAYTIME HEATING AND PERSISTENT SLY SURFACE FLOW SHOULD ALLOW RAPID DESTABILIZATION ACROSS THE REGION WITH CAPE VALUES ON THE ORDER OF 2000-3000 J/KG. THE LOW LEVEL FLOW WILL NOT BE PARTICULARLY STRONG...YET AS MASS FIELDS ADJUST TO THE NEXT TROUGH...BUT HODOGRAPHS WILL BE LONG AND WILL STRONGLY FAVOR SUPERCELLS WITH VERY LARGE HAIL FROM SERN SD EWD ACROSS NRN IA...PERHAPS SRN MN AND SWRN WI. ...NEB...SERN SD...WRN IA EVENING/OVERNIGHT... VERY STRONG INSTABILITY WILL BUILD OVER CNTRL AND ERN NEB...PRIOR TO STORMS FORMING IN THE STRONG HEATING OVER W CNTRL NEB. CELLS SHOULD QUICKLY BECOME SUPERCELLULAR WITH VERY LARGE HAIL AND DAMAGING WINDS. MODELS ARE IN GOOD AGREEMENT DEPICTING A JETLET...POSSIBLY RELATED TO CONVECTIVE FEEDBACK...MOVING FROM NEB INTO WRN IA. THIS IS LIKELY DUE TO EXPLOSIVE RELEASE OF INSTABILITY WITH STEEP LAPSE RATES AND HIGH PRECIPITABLE WATER CONTENT. THE INITIAL SUPERCELLS WILL LIKELY MERGE DURING THE EVENING...BECOMING AN MCS CAPABLE OF WIDESPREAD DAMAGING WINDS AS FAR E AS WRN IA. ...MD...ERN VA...ERN NC... STRONG HEATING IS EXPECTED ACROSS THE AREA...PERHAPS IN THE WAKE OF REMNANTS FROM THIS EVENINGS STORMS UPSTREAM OVER WV. FORECAST SOUNDINGS INDICATE THAT 1500-2000 J/KG MLCAPE WILL BE PRESENT AND NO CAPPING WILL EXIST. WITH WNWLY FLOW ALOFT...ANY STORMS THAT FORM UPSTREAM WILL HAVE THE POTENTIAL TO GROW UPSCALE INTO AN MCS CAPABLE OF BOTH WIND AND MARGINAL HAIL. ...CNTRL KS/WRN OK/NWRN TX DRYLINE... A HIGHLY CONDITIONAL SEVERE THREAT WILL EXIST BY LATER AFTERNOON ALONG THE DRYLINE. EXTREME INSTABILITY WILL BUILD UP ALONG THE DRYLINE WHERE BOUNDARY LAYER DEWPOINTS WILL RISE INTO THE UPPER 60S F BENEATH STEEP LAPSE RATES ALOFT. FORECAST SOUNDINGS SUGGEST THAT TOTAL MIXING WILL OCCUR W OF THE DRYLINE THROUGH 500 MB...WHILE THE AIR MASS E OF THE DRYLINE REMAINS CAPPED. THUS...A NARROW ZONE OF UNCAPPED AND VERY UNSTABLE AIR WILL EXIST NEAR THE DRYLINE. ..JEWELL/GARNER.. 05/02/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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