MESOSCALE PRECIPITATION DISCUSSION 0723
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
609 AM EST WED DEC 30 2015
 
AREAS AFFECTED...PORTIONS OF EAST-CENTRAL AL & NORTHERN GA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 301108Z - 301553Z
 
SUMMARY...A BATCH OF RAIN AND THUNDERSTORMS IS MOVING INTO AN AREA
OF GREATER SOIL SATURATION.  FLASH FLOODING IS POSSIBLE.

DISCUSSION...A CONSOLIDATING AREA OF SHOWERS AND THUNDERSTORMS
WITH COOLING CLOUD TOPS IS MOVING ACROSS PORTIONS OF CENTRAL AL
AHEAD OF A NEGATIVELY TILTED SHORTWAVE, HEADING TOWARDS NORTHERN
GA.  PRECIPITABLE WATER VALUES OF ~1.5" LIE ACROSS THIS REGION PER
GPS VALUES.  A POOL OF 1000+ J/KG MUCAPE LIES TO THE SOUTH, ACROSS
SOUTHWEST GA PER SPC MESOANALYSES.  INFLOW AT 850 HPA IS 35-40 KTS
AND CONVERGENT PER VAD WIND PROFILES.  HOURLY RAIN RATES VIA
SURFACE OBSERVATIONS AND RADAR IMAGERY SHOW 0.5-1" AN HOUR RATES.

THE MESOSCALE QPF GUIDANCE THAT IS CAPTURING THIS ACTIVITY THE
BEST (A NORTHWARD-ADJUSTED COMPROMISE OF THE 09Z HRRR, 00Z
WRF4NSSL, AND 08Z HRRR EXPERIMENTAL) INDICATE THAT LOCAL AMOUNTS
IN THE 2-4" RANGE ARE POSSIBLE THROUGH 16Z -- THIS RAIN COULD FALL
QUICKLY.  WHILE GFS-BASED GALVEZ-DAVISON INDEX VALUES ARE
INCREASING, THEY DO NOT PASS 30, WHICH INDICATES THAT POSSIBLE
WORDING IS BEST.  THIS DEGREE OF MOISTURE SUPPORTS HOURLY RAIN
RATES UP TO 2", WHICH IS MOST LIKELY WHERE CELLS MERGE AND/OR
TRAIN.  THESE SORT OF HOURLY RATES WOULD BE MOST PROBLEMATIC IN
URBAN AREAS.  FLASH FLOOD GUIDANCE VALUES IN THIS AREA ARE MODEST
DUE TO RECENT RAINS.

ROTH

ATTN...WFO...BMX...CAE...FFC...GSP...

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

LAT...LON   34938324 33738218 32688476 32368659 33218660 
            34758526