MESOSCALE PRECIPITATION DISCUSSION 0002
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1249 AM EST SUN JAN 04 2015
 
AREAS AFFECTED...SOUTHERN AND EASTERN AL & NORTHWEST GA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 040548Z - 041148Z
 
SUMMARY...CONVECTIVE BANDS HAVE SHOWN INCREASING RAINFALL RATES AS
OF LATE WITHIN AN AREA OF DEEP SOUTHWESTERLY FLOW ACROSS AL AND
SOUTHERN MS.  FLASH FLOODING IS POSSIBLE, AS RAIN RATES
APPROACHING 2" AN HOUR COULD OCCUR WITHIN AN AREA OF SATURATING
SOILS.

DISCUSSION...A 05Z SURFACE ANALYSIS REVEALED A SLOW-MOVING COLD
FRONT ACROSS EASTERN MS, WITH A WARM FRONT CUTTING ACROSS CENTRAL
AL AND CENTRAL GA.  A COUPLE LOOSELY ORGANIZED CONVECTIVE LINES
LIE AHEAD OF THIS FRONT WITHIN A REGION OF 1.50-1.75" PRECIPITABLE
WATER VALUES (2-3 SIGMAS ABOVE NORMAL FOR EARLY JANUARY).  RECENT
RADAR RETURNS INDICATE INCREASING RAINFALL RATES, TOWARDS 2" AN
HOUR IN CENTRAL AL, WITH SATELLITE IMAGERY SHOWING UNIFORMLY WARM
CLOUD TOPS.  AREA 00Z SOUNDINGS REVEAL FREEZING LEVELS IN THE
11-12,000 FOOT RANGE ABOVE GROUND LEVEL, WHICH ADDS CONFIDENCE TO
THE IDEA THAT WARM RAIN PROCESSES ARE AT PLAY.  INFLOW AT 850 HPA
IS CLOSE TO THE MEAN 850-400 HPA WINDS, NEAR 55 KTS PER AREA VAD
WIND PROFILES.  CAPE VALUES PER RECENT SPC MESOANALYSES SHOW AN
UPTICK ACROSS SOUTHERN AL, WHICH COULD BE FUELING THE INCREASED
RAIN RATES.

THE 00Z MESOSCALE GUIDANCE INCREASED THEIR QPF EXPECTATIONS FROM
THEIR PRIOR RUNS IN THIS REGION, INDICATING 2-3" OF RAIN OVER THE
NEXT SEVERAL HOURS, THOUGH THEIR AXES APPEAR TOO FAR NORTHWEST
BASED ON RECENT RADAR IMAGERY.  FRONTOGENESIS FIELDS AND 850 HPA
WIND FIELDS WITHIN RECENT RAP RUNS INDICATE SOME PROGRESSION TO
THE EAST IS POSSIBLE OVER THE NEXT SEVERAL HOURS, POTENTIALLY
FORCED BY THE STRONG LOW LEVEL INFLOW.  RECENT AND ONGOING RAINS
ARE SATURATING AREA SOILS.  CELL TRAINING COULD LEAD TO FLASH
FLOODING IN THIS REGION OVER THE NEXT SIX HOURS SINCE THE UPSTREAM
COLD FRONT REMAINS SLOW-MOVING.  FLASH FLOODING IS CONSIDERED
POSSIBLE IN THIS REGION.

ROTH

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

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

LAT...LON   34278499 33658451 31458611 30388723 30398895 
            31788823 33668655