SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0100 AM CDT TUE MAY 29 2012 VALID 291200Z - 301200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM SRN KS/SWRN MO SWD INTO N TX... ...THERE IS A SLGT RISK OF SVR TSTMS FROM WRN NEW ENGLAND SWWD ACROSS THE UPPER OH VALLEY AREA... ...SYNOPSIS... AN UPPER TROUGH INITIALLY CENTERED OVER WRN ONTARIO AND THE ADJACENT UPPER MS VALLEY/WRN UPPER GREAT LAKES PORTION OF THE U.S. WILL SHIFT STEADILY EWD THIS PERIOD...REACHING A POSITION OVER QUEBEC AND THE NORTHEAST U.S. BY 30/12Z. MEANWHILE IN THE WEST...A MUCH MORE COMPACT UPPER FEATURE INITIALLY OVER SRN BRITISH COLUMBIA/WA IS FORECAST TO SLIDE ESEWD INTO MT BY THE END OF THE PERIOD. AT THE SURFACE...A WEAK COLD FRONT ASSOCIATED WITH THE N CENTRAL/NERN U.S. TROUGH IS PROGGED TO CROSS THE LOWER GREAT LAKES/OH VALLEY THROUGH THE DAY. BY LATE AFTERNOON...THE FRONT SHOULD EXTEND FROM ERN NY/WRN NEW ENGLAND SWWD ACROSS THE OH VALLEY REGION INTO THE KS/OK VICINITY. THIS FRONT -- AND A DRYLINE EXTENDING SWD ACROSS WRN OK/TX DURING THE AFTERNOON -- WILL BE FOCI FOR STRONG/SEVERE AFTERNOON AND EVENING CONVECTION. ...SRN KS/OK/N TX AND VICINITY... DAYTIME HEATING OF THE MOIST LOW-LEVEL AIRMASS COMBINED WITH EWD ADVECTION OF VERY STEEP MID-LEVEL LAPSE RATES WILL RESULT IN STRONG DESTABILIZATION THROUGH THE AFTERNOON ACROSS PARTS OF KS AND THE SRN PLAINS...WITH MIXED-LAYER CAPE OF 1500 TO 2500 J/KG WIDESPREAD...AND LIKELY EXCEEDING 3000 J/KG IN PARTS OF OK AND VICINITY. WHILE THIS WILL PROVIDE A VERY FAVORABLE THERMODYNAMIC ENVIRONMENT FOR POTENT CONVECTIVE DEVELOPMENT...STORM COVERAGE MAY BE SOMEWHAT LIMITED BY WEAK RIDGING ALOFT AND LACK OF A WELL-DEFINED UPPER FEATURE. STILL...LIKELY PRESENCE OF A WARM FRONT INVOF THE KS/OK BORDER REGION AND A DRYLINE MIXING EWD ACROSS WRN OK/WRN TX SUGGEST THAT ISOLATED STORM DEVELOPMENT SHOULD OCCUR DURING THE AFTERNOON -- MOST LIKELY INITIALLY INVOF THE DRYLINE/FRONT INTERSECTION EXPECTED INVOF SWRN KS/NWRN OK DURING THE AFTERNOON. ONCE STORMS DEVELOP...UPSCALE GROWTH IS EXPECTED ALONG OUTFLOWS GIVEN STRONG INSTABILITY. RESULTING COMPLEX STORMS STRUCTURES ARE ANTICIPATED...THOUGH SHEAR SUPPORTIVE OF SUPERCELLS WILL SUPPORT LARGE ROTATING STORMS AT TIMES. GIVEN THE DEGREE OF INSTABILITY AND SHEAR...STORMS WHICH CAN ORGANIZE AND REMAIN SOMEWHAT ISOLATED WILL BE CAPABLE OF PRODUCING VERY LARGE HAIL...AND LOCALLY DAMAGING WINDS WILL BECOME INCREASINGLY LIKELY IF STORMS CONGEAL INTO ONE OR MORE SMALL BOWING MCS/S. AN ISOLATED TORNADO OR TWO ALSO WILL BE POSSIBLE -- MOST LIKELY INVOF THE WARM FRONT OVER THE NRN OK VICINITY. MORE ISOLATED CELLS SHOULD DEVELOP SWD ALONG THE DRYLINE...AND ALSO BECOME CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WINDS LOCALLY. OVERNIGHT...STORMS SHOULD MOVE EWD/SEWD ACROSS PARTS OF OK/N TX WITH SOME ATTENDANT SEVER POTENTIAL...BEFORE DIMINISHING LATER IN THE PERIOD. ...WRN NEW ENGLAND SWWD ACROSS THE UPPER OH VALLEY REGION... A WARM/MOIST/DESTABILIZING AIRMASS IS FORECAST TO BE EVOLVING BY MIDDAY AHEAD OF THE ADVANCING COLD FRONT ACROSS THE NORTHEAST/MIDWEST REGION. AS THE FRONT -- AND ASSOCIATED UPPER TROUGH -- PROGRESS EWD WITH TIME...SHOWERS AND THUNDERSTORMS ARE FORECAST TO INCREASE WITHIN MULTIPLE BANDS...CROSSING OH AND SHIFTING INTO PA/NY/WRN NEW ENGLAND THROUGH THE AFTERNOON. EVENTUALLY...BANDS OF STORMS SHOULD CROSS THE APPALACHIANS AND MOVE INTO SRN NEW ENGLAND AND THE MID-ATLANTIC REGION. WHILE THE STRONGEST FLOW ALOFT WILL REMAIN WELL W OF THE SURFACE COLD FRONT...AMPLE SHEAR -- PARTICULARLY ACROSS NRN PORTIONS OF THE RISK AREA -- WILL SUPPORT THREATS FOR DAMAGING WINDS AND HAIL. THE THREAT SHOULD LINGER INTO THE EVENING BEFORE DIMINISHING WITH DIURNAL STABILIZATION. ..GOSS.. 05/29/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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