SWODY1
SPC AC 171624
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1124 AM CDT THU SEP 17 2009
VALID 171630Z - 181200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A RATHER STAGNANT PATTERN WILL PERSIST OVER THE CONUS THROUGH
TONIGHT...WITH THE PRIMARY BELT OF WESTERLIES CONFINED TO NEAR AND N
OF THE U.S./CANADIAN BORDER. THE MORE ACTIVE CONVECTIVE REGIONS
WILL BE ASSOCIATED WITH THE SLOW-MOVING...VERTICALLY STACKED LOW
OVER E TX...AND A SEPARATE LOW OVER ERN AZ. BANDS OF CONVECTION
WILL CONTINUE THROUGH THE DAY TO THE N OF THE CYCLONE CENTER FROM NE
TX ENEWD INTO NRN MS/AL AND TN...ALONG A WEAK BAROCLINIC ZONE...AS
WELL AS WITHIN THE WARM SECTOR AND THE DEEP MOISTURE PLUME FROM SE
LA EWD ACROSS MS/AL/S GA. RATHER WEAK MID LEVEL LAPSE RATES AND
LOW-MID LEVEL VERTICAL SHEAR SUGGEST THAT ANY SEVERE STORM THREAT
ACROSS THE GULF COAST WILL BE TOO MARGINAL TO WARRANT THE INCLUSION
OF WIND/HAIL PROBABILITIES.
A SOMEWHAT GREATER THREAT FOR STRONG/ISOLATED SEVERE STORMS IS AGAIN
EXPECTED THIS AFTERNOON IN ASSOCIATION WITH THE MID LEVEL LOW
DRIFTING SSEWD OVER ERN AZ. A BELT OF 25-50 KT MID-UPPER WLY FLOW
TO THE S OF THE LOW...AS WELL AS AN INFLUX OF BOUNDARY LAYER
DEWPOINTS IN THE MID 50S FROM THE E...WILL CONTRIBUTE TO SUFFICIENT
INSTABILITY AND VERTICAL SHEAR FOR ORGANIZED MULTICELL CLUSTERS AND
MARGINAL SUPERCELL STRUCTURES. ISOLATED HAIL AND WIND GUSTS NEAR
SEVERE CRITERIA WILL BE POSSIBLE THIS AFTERNOON IN THE AREA OF
STRONGER INSTABILITY ON THE W EDGE OF THE THICKER CLOUDS AND RICHER
MOISTURE.
..THOMPSON/SMITH.. 09/17/2009
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