MESOSCALE DISCUSSION 2042 NWS STORM PREDICTION CENTER NORMAN OK 0953 AM CDT THU AUG 07 2008 AREAS AFFECTED...PARTS OF NRN/CNTRL AL AND GA CONCERNING...SEVERE POTENTIAL...WATCH LIKELY VALID 071453Z - 071630Z THE RISK FOR LOCALIZED DAMAGING DOWNBURSTS WILL EXIST AS STORMS INCREASE ACROSS PARTS OF THE TENNESSEE VALLEY AND THE GULF STATES LATE THIS MORNING/AFTERNOON. TRENDS ARE BEING MONITORED FOR THE POSSIBILITY OF A MORE ORGANIZED SEVERE THREAT AND THE POSSIBILITY OF A WW. A SMALL CLUSTER OF STORMS...NOW SPREADING INTO AREAS NEAR/NORTH OF MUSCLE SHOALS/FLORENCE AL...APPEARS TO BE SUPPORTED BY AN AREA OF STRONGER FORCING FOR UPWARD VERTICAL MOTION ON THE SOUTHERN FRINGE OF THE LARGER SCALE TROUGH CURRENTLY AMPLIFYING ACROSS THE EASTERN STATES. MODELS ARE SUGGESTIVE THAT THIS FORCING WILL CONTINUE EAST SOUTHEASTWARD THROUGH NORTHERN ALABAMA AND GEORGIA BETWEEN NOW AND 18-19Z. AS THIS OCCURS...COINCIDENT WITH STRONGER HEATING/DESTABILIZATION OF A MOIST BOUNDARY LAYER...CHARACTERIZED BY SURFACE DEW POINTS NEAR 70F...EXPANSION AND INTENSIFICATION OF THE ONGOING STORM CLUSTER APPEARS PROBABLE INTO/THROUGH EARLY AFTERNOON. MIXED LAYER CAPE ON THE ORDER OF 1000-2000 J/KG WILL PROMOTE VIGOROUS UPDRAFTS CAPABLE OF PRODUCING SMALL HAIL AND LOCALLY HEAVY RAINFALL IN THE PRESENCE OF HIGH PRECIPITABLE WATER. AND...THIS WILL BE ACCOMPANIED BY INCREASING POTENTIAL FOR A STRENGTHENING COLD POOL. IF THIS OCCURS...20 KT DEEP LAYER WESTERLY MEAN FLOW ON THE SOUTHERN FRINGE OF THE UPPER TROUGH WILL CONTRIBUTE TO MODERATE FORWARD STORM PROPAGATION...ALONG WITH AN ENHANCED RISK FOR POTENTIALLY DAMAGING WINDS ALONG ITS GUST FRONT. THIS COULD AFFECT PARTS OF THE ATLANTA METROPOLITAN AREA AS EARLY AS 18-20Z.
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