SPC AC 091231
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0731 AM CDT WED SEP 09 2009
VALID 091300Z - 101200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A QUIESCENT LARGE SCALE REGIME IS EXPECTED ACROSS THE CONUS THROUGH
TONIGHT. AN INITIAL NRN STREAM SHORTWAVE TROUGH IS MOVING NEWD OVER
WRN ONTARIO...AROUND A RIDGE OVER THE UPPER GREAT LAKES/SW
ONTARIO/SW QUEBEC. AN ASSOCIATED/TRAILING SURFACE FRONT FROM NRN MN
TO CENTRAL NEB WILL BECOME DIFFUSE WITH TIME...AND BEGIN TO RETREAT
NWD OVERNIGHT IN RESPONSE TO WEAK LEE CYCLOGENESIS ACROSS THE NRN
HIGH PLAINS...IN ADVANCE OF ANOTHER NRN STREAM SHORTWAVE TROUGH
PROGRESSING EWD FROM THE PAC NW COAST. ELSEWHERE...A WEAK MEAN FLOW
REGIME WILL PERSIST OVER MUCH OF THE CONUS...WITH EMBEDDED MID LEVEL
VORTICITY CENTERS OVER WRN/CENTRAL TX WITH THE SUBTROPICAL JET...AND
A RESIDUAL MCV WITH ONGOING CONVECTION OVER SE KS/SW MO. AN
ISOLATED LARGE HAIL OR DAMAGING WIND EVENT CANNOT BE RULED OUT
ACROSS A RELATIVELY BROAD AREA OF THE S CENTRAL STATES...BUT THE
THREAT APPEARS TOO LIMITED TO WARRANT A LARGE AREA OF LOW
PROBABILITIES. A SOMEWHAT GREATER THREAT FOR SEVERE STORMS IS
EXPECTED THIS AFTERNOON IN CONJUCTION WITH THE LINGERING MID LEVEL
LOW OVER THE OH VALLEY AND SRN APPALACHIANS AREA.
...SRN APPALACHIANS AND SAVANNAH RIVER VALLEY TODAY...
THE SLOW-MOVING CLOSED LOW...WITH A PRIMARY CIRCULATION CENTER OVER
ERN KY THIS MORNING...WILL CONTINUE TO DRIFT SEWD OVER THE SRN
APPALACHIANS THROUGH THIS EVENING. THOUGH THERE IS LITTLE SURFACE
REFLECTION OF THE MID LEVEL LOW...IT WILL STILL HELP FOCUS
THUNDERSTORM DEVELOPMENT TODAY WHERE WEAK ASCENT COINCIDES WITH
DAYTIME HEATING OF A BOUNDARY LAYER WITH LOW-MID 60S DEWPOINTS. THE
COMBINATION OF RELATIVELY STEEP LOW-MID LEVEL LAPSE RATES WITH
DAYTIME HEATING...THE MID LEVEL COLD POOL /-12 TO -14 C AT 500
MB/...AND A BELT OF ENHANCED MID-UPPER WNWLY FLOW ON THE WRN AND SRN
PERIPHERY OF THE LOW WILL SUPPORT A FEW ORGANIZED MULTICELL/MARGINAL
SUPERCELL STORMS CAPABLE OF PRODUCING ISOLATED DAMAGING GUSTS AND
HAIL NEAR SEVERE LIMITS.
..THOMPSON/GARNER.. 09/09/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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