Bottom line is that some of the storms today over West Central, North Central and Northeast Alabama could become severe with the potential for damaging winds, hail and even a potential small tornado. No weather watch is expected at this time.
Flooding continues to be a significant threat.
MESOSCALE DISCUSSION 2031
NWS STORM PREDICTION CENTER NORMAN OK
1025 AM CDT SAT SEP 26 2009
AREAS AFFECTED…PORTIONS NWRN GA…CENTRAL/NERN AL…PARTS OF SRN
MIDDLE TN AND SERN TN.
CONCERNING…SEVERE POTENTIAL…WATCH UNLIKELY
VALID 261525Z – 261730Z
ISOLATED STG-SVR GUSTS AND MRGL HAIL ARE POSSIBLE WITH TSTMS OVER
DISCUSSION AREA. TORNADO POTENTIAL APPEARS VERY CONDITIONAL BUT
CANNOT BE RULED OUT…ESPECIALLY WHERE RELATIVELY DISCRETE CELLS
INTERACT WITH BOUNDARIES DESCRIBED BELOW.
SFC MESOANALYSIS INDICATED COLD FRONT EXTENDING FROM LOW OFFSHORE
SC…WWD ACROSS EXTREME SRN SC…NEAR SAV…WNWWD ACROSS MCN AREA
THEN NWWD THROUGH ATL/CHA AREAS..BECOMING DIFFUSE NWD ACROSS ERN TN
AMIDST EXTENSIVE PRECIP AND EMBEDDED TSTMS. FRONT STILL IS MOVING
SWWD 5-10 KT ACROSS GA BUT SHOULD DECELERATE THROUGH REMAINDER
MORNING AND AFTERNOON. SEVERAL CONVECTIVE BANDS/BOUNDARIES ARE
EVIDENT FROM MIDDLE-ERN TN SWWD ACROSS AL AND MS…PRIMARY ONE BEING
FROM NEAR CHA SWWD ACROSS MARSHALL/JEFFERSON/TUSCALOOSA COUNTIES
AL…INTERSECTING ANOTHER BAND MOVING NEWD ACROSS LAMAR/PICKENS
COUNTY AL. ASSOCIATED BOUNDARY EXTENDS SWWD OVER NOXUBEE/MADISON
COUNTIES MS. THESE BOUNDARIES SHOULD UNDERGO NET EWD MOTION THROUGH
EARLY AFTERNOON. AIR MASS E OF CONVECTIVE BOUNDARIES…AND W OF
FRONT…IS EXPECTED TO CONTINUE HEATING/DESTABILIZING THROUGH
MID-AFTERNOON…WITH 70S DEW POINTS CONTRIBUTING TO 1000-2000 J/KG
MLCAPE IN RELATIVELY CLOUD-FREE AREAS. HOWEVER…DEEP-LAYER SHEAR
WILL WEAKEN CONSIDERABLY WITH SWD EXTENT…LEAVING FAIRLY NARROW
CORRIDOR ACROSS CENTRAL AL AND NWRN GA WHERE SRN RIM OF STRONGER
FLOW ALOFT IS JUXTAPOSED WITH OPTIMALLY HIGH-THETAE AIR MASS.
POCKET OF RELATIVELY UNMODIFIED AIR ALSO IS EVIDENT OVER PORTIONS
SRN MIDDLE TN…SERN TN AND NERN AL. CLOUD COVER OVER THIS AREA
WILL ENSURE THAT HEATING WILL NOT BE AS STG AS FARTHER S ACROSS
AL/GA…HOWEVER MODIFIED RAOBS AND RUC SOUNDINGS SUGGEST ESSENTIALLY
UNCAPPED AIR MASS WITH PARCELS SFC-BASED AND 500-1000 J/KG MLCAPE.
LOW LEVEL FLOW WILL REMAIN WEAK ACROSS MOST OF THIS AREA…KEEPING
HODOGRAPHS SMALL. HOWEVER…ENHANCED BACKING/VORTICITY SHOULD EXIST
ALONG DAMMING FRONT FROM SERN TN ACROSS NW GA…AND ALONG AL
CONVECTIVE BOUNDARY. THESE BOUNDARIES MAY BE FOCI FOR AT LEAST BRIEF
SUPERCELLULAR EVOLUTION FOR CELLS INTERACTING WITH THEM…AS WITH
EARLIER TSTM W BHM.
..EDWARDS.. 09/26/2009
