MESOSCALE PRECIPITATION DISCUSSION 0504
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
149 AM EDT TUE SEP 22 2015
 
AREAS AFFECTED...C & SW GEORGIA...SE ALABAMA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 220548Z - 220948Z
 
SUMMARY...POCKETS OF HIGHLY EFFICIENT VERY SLOW MOVING CELLS
CAPABLE OF RATES IN THE 1.5-2"/HR RANGE.

DISCUSSION...
WV/IR LOOP SHOWS IMPRESSIVE IF SHALLOW LOOKING COMMA/HOOK OF
SHORTWAVE AT THE BASE OF ELONGATED TROF.  VORT CENTER OVER SE AL
ALLOWING FOR DECENT PVA ALONG WITH SLIGHTLY DIFFLUENT FLOW ALOFT
AND PASSING 50KT 3H JET STREAK INCREASING EVACUATION ALOFT TO
MAINTAIN CONVECTIVE CORES. IN THE LOW LEVELS FLOW IS GENERALLY
WEAK BUT JUST ABOVE THE BOUNDARY LAYER 10-15 KT EASTERLY FLOW
SIPHONING OFF STRONGER OFF SHORE FLOW IS ALLOWING FOR SOME
INCREASE IN MOISTURE FLUX AND INSTABILITY TRANSPORT WITH MUCAPES
ANALYZED OVER 1000 J/KG.  CONVERGENCE AT THE SFC ALIGNED WITH
CONFLUENCE OF NNELY FLOW OUT OF CENTRAL SC FROM WASHINGTON/WILKENS
COUNTY BACK TOWARD SW AL SUPPORTS SOME CONTINUED IF WEAK CELL
INFLOW FOR SOME MAINTENANCE.  RATES WILL BE MODEST RANGING FROM
1.5-2"/HR...BUT GIVEN WEAK STEERING FLOW...CELL MOTION VECTORS ARE
5 KTS OR SO TO ALLOW FOR COMPOUNDING TOTALS.  HOWEVER...LIMITED
INFLOW AND FFG VALUES IN EXCESS OF 3"/3HRS...ANY FLASH FLOOD
THREAT WILL BE HIGHLY LOCALIZED AND LIKELY NEARER UPPER LEVEL
SUPPORT OVER SW AL AND E GA THROUGH THE EARLY MORNING HOURS.   

HI-RES CAMS HAVE NOT BEEN VERY ADEPT AT HANDLING THIS CONVECTION
EXCEPT FOR CELLS PROPAGATING SW ALONG A STRONGER OUTFLOW BOUNDARY
FROM CENTRAL SC INTO E GA THIS REDUCES CONFIDENCE THOUGH
OBS/VWP/RADAR AND SATELLITE ALL SUGGEST CONTINUED THREAT FOR THE
NEXT FEW HOURS.     

ATTN...WFO...BMX...CAE...FFC...TAE...

ATTN...RFC...SERFC...

LAT...LON   33808285 33218209 32808231 31658362 31088490 
            31138585 31688573 32458515 33408394