MESOSCALE PRECIPITATION DISCUSSION 0688
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1201 AM EST THU DEC 24 2015
 
AREAS AFFECTED...WESTERN FL PANHANDLE...SOUTHEAST AL...WESTERN GA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 240450Z - 240930Z
 
SUMMARY...HEAVY CONVECTIVE RAINFALL WILL CONTINUE OVERNIGHT AS
TRAINING SHOWERS AND THUNDERSTORMS CONTINUE.

DISCUSSION...THE LATEST IR SATELLITE IMAGERY SHOWS A SW/NE AXIS OF
RATHER RAPIDLY COOLING CONVECTIVE TOPS ACROSS SOUTHEAST AL AND
INTO PARTS OF WESTERN GA. THE CONVECTION IS EMBEDDED WITHIN A
BROADLY DIFFLUENT UPPER AIR PATTERN AS SUGGESTED BY IR/WV
SATELLITE IMAGERY AND APPEARS TO BE FOCUSING ALONG A WEAK SURFACE
CONVERGENCE ZONE THAT EXTENDS FROM THE WESTERN FL PANHANDLE
NORTHEAST ACROSS SOUTHEAST AL AND INTO WESTERN GA.

THE AIRMASS IS ALREADY VERY MOIST WITH PWATS RUNNING BETWEEN 1.6
TO 1.7 INCHES AND THIS IS EXPECTED TO FAVOR RAINFALL RATES OF 1 TO
2 INCHES/HR. GIVEN THE DEEP LAYER SOUTHWEST FLOW RUNNING PARALLEL
TO THE SURFACE CONVERGENCE ZONE...TRAINING CONVECTION WILL BE THE
MAIN CONCERN OVERNIGHT.

THE CAM GUIDANCE INDICATES A WELL-DEFINED SIGNAL FOR TRAINING
CONVECTION IN A SW/NE FASHION...AND SUGGEST SOME PERSISTENCE TO
THE CONVECTION GIVEN AT LEAST SOME MODEST DEEP LAYER ASCENT
AFFORDED BY WEAK UPPER LEVEL JET FORCING.

MULTIPLE RUNS OF THE HRRR OVER THE LAST FEW HOURS...AND THE 00Z
ARW AND 00Z NMMB SHOW ADDITIONAL HEAVY RAINS FOCUSING OVER
SOUTHEAST AL IN PARTICULAR...AND GIVEN RECENT HEAVY RAINFALL...ANY
ADDITIONAL RAINS MAY RESULT IN FLASH FLOODING.

EXPECT ADDITIONAL RAINFALL AMOUNTS THROUGH THE PREDAWN HOURS OF AS
MUCH AS 3 TO 5 INCHES AT LEAST LOCALLY. WILL CONTINUE TO MONITOR.

ORRISON

ATTN...WFO...BMX...FFC...MOB...TAE...

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

LAT...LON   33258484 33078392 31788498 31058565 30478635 
            30498694 30948706 31968622