DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 261242
SWODY1
SPC AC 261240

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0740 AM CDT SUN SEP 26 2010

VALID 261300Z - 271200Z

...NO SVR TSTM AREAS FORECAST...

...NE GULF/SE ATLANTIC STATES THROUGH TONIGHT...
THE DEVELOPING CLOSED LOW OVER THE MID MS VALLEY WILL CONTINUE TO
DIG SSEWD TOWARD THE NRN MS AREA BY LATE TONIGHT...WHILE SURFACE
CYCLOGENESIS OCCURS TONIGHT ALONG A PRE-EXISTING BAROCLINIC ZONE
FROM THE NE GULF COAST INTO CENTRAL/NRN GA. A BROAD MOIST SECTOR IS
ALREADY PRESENT ACROSS THE GULF AND SE ATLANTIC COASTAL
PLAINS...WHERE BOUNDARY LAYER DEWPOINTS IN THE LOWER 70S SHOULD BE
MAINTAINED THROUGH TONIGHT WITH ONSHORE FLOW. A 30-40 KT LLJ IS
FORECAST TO DEVELOP NEWD FROM THE NE GULF COAST TO THE PIEDMONT OF
THE CAROLINAS IN CONJUNCTION WITH THE SURFACE CYCLOGENESIS...AND
THIS PROCESS WILL CONTRIBUTE TO STRONGER LOW-LEVEL SHEAR AND MORE
FAVORABLE HODOGRAPHS FOR SUPERCELLS TONIGHT FROM THE FL PANHANDLE
NEWD INTO GA.

RELATIVELY WEAK LOW-MIDLEVEL FLOW/SHEAR AND WEAK INSTABILITY SHOULD
KEEP THE DAMAGING WIND/TORNADO THREATS QUITE LIMITED DURING THE DAY
ACROSS THE NE GULF COAST AS SEVERAL THUNDERSTORM CLUSTERS SPREAD
INLAND...AS WELL AS ALONG THE STALLED BAROCLINIC ZONE ACROSS THE
PIEDMONT. DESPITE BEING OUT OF PHASE WITH THE DIURNAL CYCLE...THE
MOIST BOUNDARY LAYER WILL HELP MAINTAIN WEAK INSTABILITY OVERNIGHT
AS THE LLJ STRENGTHENS. A REMAINING CONCERN TONIGHT WILL STILL BE
WEAK BUOYANCY AS A RESULT OF POOR MIDLEVEL LAPSE RATES AND
RELATIVELY WIDESPREAD RAINFALL. OTHER CONCERNS CENTER ON THE
MAGNITUDE OF THE LOW-LEVEL FLOW RESPONSE /THE 06Z NAM IS MOST
AGGRESSIVE...WHILE THE OTHER SHORT-RANGE MODELS SHOW A SOMEWHAT
WEAKER LLJ/...AND THE TENDENCY FOR THE STRONGER DEEP-LAYER
FLOW/SHEAR TO LAG W OF THE WARM SECTOR. THUS...IT APPEARS
APPROPRIATE TO MAINTAIN LOW TORNADO AND DAMAGING WIND PROBABILITIES
FROM N FL NEWD INTO THE CAROLINAS...PRIMARILY FOR TONIGHT.
STILL...AN UPGRADE TO SLIGHT RISK IN LATER UPDATES FOR A PORTION OF
THIS AREA IS NOT OUT OF THE QUESTION...ASSUMING THE MORE AGGRESSIVE
NAM FORECAST VERIFIES.

..THOMPSON/GARNER.. 09/26/2010

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