SPC AC 041228
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0728 AM CDT WED OCT 04 2006
VALID 041300Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS TODAY FOR THE OH VALLEY/SRN
LOWER MI INTO WRN/CENTRAL NY...
...OH VALLEY TO NY TODAY...
A POSITIVE TILT MID-UPPER LEVEL TROUGH WITH EMBEDDED VORTICITY
CENTERS OVER ERN NEB AND SERN MN WILL CONTINUE EWD OVER THE MS
VALLEY THIS MORNING...AND CROSS THE OH VALLEY BY EARLY TONIGHT.
THIS MID LEVEL WAVE WILL BE ACCOMPANIED BY A SURFACE CYCLONE THAT IS
FORECAST TO DEVELOP EWD FROM LAKE HURON THIS MORNING TO MAINE BY
LATE EVENING...WHILE A TRAILING COLD FRONT MOVES EWD ACROSS NEW
ENGLAND AND SEWD ACROSS THE OH VALLEY.
STRONG/ISOLATED SEVERE STORMS CONTINUE THIS MORNING IN A BAND ALONG
THE FRONT FROM SE WI INTO LOWER MI. THIS CONVECTION WILL LIKELY
PERSIST THROUGH THE MORNING IN ASSOCIATION WITH LOW-LEVEL
FRONTOGENESIS...AS WELL AS DIFFERENTIAL CVA IN ADVANCE OF THE SE MN
TROUGH...AND THE RIGHT ENTRANCE REGION OF THE UPPER JET OVER
ONTARIO/QUEBEC. REMNANT MID LEVEL PLUME OF STEEP LAPSE RATES FROM
THE PLAINS AND BOUNDARY LAYER DEWPOINTS IN THE LOW-MID 60S ALONG AND
S OF THE FRONT WILL CONTRIBUTE TO MUCAPE VALUES OF 1500-2000 J/KG.
THIS INSTABILITY...ALONG WITH EFFECTIVE BULK SHEAR IN EXCESS OF 40
KT...WILL SUPPORT A THREAT FOR AT LEAST ISOLATED LARGE HAIL AND
POSSIBLY DAMAGING WIND GUSTS WITH STORMS NEAR AND N OF THE FRONT
THROUGH MID MORNING.
BY MIDDAY TO EARLY AFTERNOON...THE STRONGER SURFACE-BASED
INSTABILITY /MLCAPE VALUES NEAR 1500 J/KG/ IS EXPECTED S OF THE
FRONT OVER INDIANA/OH IN PROXIMITY TO THE MOISTURE AND LAPSE RATE
SOURCE REGIONS...WITH WEAKER INSTABILITY FARTHER NE INTO NY.
HOWEVER...VERTICAL SHEAR SHOULD BE STRONGEST NEAR THE SURFACE LOW IN
NY/NEW ENGLAND. THE RATHER POOR PHASING OF WARM SECTOR INSTABILITY
AND VERTICAL SHEAR BY AFTERNOON SUGGESTS THAT MARGINALLY SEVERE
HAIL/WIND WILL BE THE MAIN THREATS WITH PRIMARILY MULTICELL STORM
CLUSTERS/LINES. WIND PROFILES WILL BE MORE FAVORABLE FOR BOWING
SEGMENTS OR SUPERCELLS CLOSE TO THE SURFACE LOW TRACK...BUT THE
SEVERE THREAT HERE WILL BE LIMITED SOMEWHAT BY WEAK INSTABILITY.
THE SEVERE STORM THREAT SHOULD END BY LATE EVENING AS WARM SECTOR
INSTABILITY DIMINISHES.
...ID/ERN ORE TODAY...
A SPEED MAX AND ASSOCIATED MID LEVEL DRYING ARE MOVING NWD FROM NV
TOWARD SW ID...AROUND THE NERN PERIPHERY OF A BROAD CLOSED LOW JUST
OFF THE CENTRAL/NRN CA COAST. SOME CONVECTION WILL CONTINUE THROUGH
THE DAYTIME DOWNSTREAM FROM THIS SPEED MAX...WHILE DRYING WILL LIMIT
THE THUNDERSTORM THREAT INTO PARTS OF SW ID. OTHERWISE...DAYTIME
HEATING/DESTABILIZATION MAY SUPPORT ISOLATED-WIDELY SCATTERED
THUNDERSTORM DEVELOPMENT LATER TODAY ACROSS ID INTO ERN ORE. THOUGH
INSTABILITY WILL BE RATHER MODEST...RELATIVELY STEEP LAPSE RATES AND
DEEP LAYER VERTICAL SHEAR MAY BE SUFFICIENT FOR ISOLATED STORMS WITH
HAIL/GUSTY WINDS.
..THOMPSON/TAYLOR.. 10/04/2006
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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