MESOSCALE PRECIPITATION DISCUSSION 0700
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1010 PM EST FRI DEC 25 2015
 
AREAS AFFECTED...PORTIONS OF THE DEEP SOUTH 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 260310Z - 260610Z
 
SUMMARY...THUNDERSTORMS WITH HEAVY RAINFALL ACROSS AL, MS, AND LA
COULD CAUSE PROBLEMS OVER SATURATED AREAS.

DISCUSSION...AN OUTFLOW BOUNDARY IS ACTING AS THE FOCUS FOR
THUNDERSTORMS ACROSS NORTHERN LA AND CENTRAL AL AT THE PRESENT
TIME.  INFLOW AT 850 HPA IS 30 KTS PER RECENT VAD WIND PROFILES. 
GPS INFORMATION INDICATES THAT PRECIPITABLE WATER VALUES OF
1.7-1.8" LURK ACROSS THE REGION, WHICH IS 2.5-3 SIGMAS ABOVE THE
NORM FOR LATE DECEMBER.  SPC MESOANALYSES INDICATE MUCAPES OF
1000-2000 J/KG ACROSS MUCH OF AL, SOUTHERN MS, AND SOUTHWEST AL. 
THUNDERSTORMS HAVE BEEN MOVING EAST-NORTHEAST NEAR AND NORTH OF
THE BOUNDARY AT ~25 KTS, WITH THE DIRECTION OF MOTION A COMPROMISE
OF THE FORWARD PROPAGATING CONVECTIVE VECTORS AND 1000-500 HPA
THICKNESS PATTERN.

A COMPROMISE OF THE 12Z ARW, 12Z SPCWRF, AND 01Z HRRR SEEM MOST
CLUED IN TO THE ONGOING CONVECTIVE EVOLUTION.  THE 18Z SSEO
NEIGHBORHOOD PROBABILITIES OF EXCEEDING THE THREE HOUR FLASH FLASH
GUIDANCE INDICATE A SHIFT IN THE HEAVIER ACTIVITY AWAY FROM AL
WITH TIME AND TOWARDS LA/MS WHERE THE LOW-LEVEL INFLOW IS MORE
ORTHOGONAL TO THE SURFACE BOUNDARY AND THE THICKNESS PATTERN SHOWS
GREATER DIVERGENCE.  LOCAL AMOUNTS OF 3-5" ARE BEING ADVERTISED BY
THE GUIDANCE BETWEEN NOW AND 09Z.  CONSIDERING SATURATED
CONDITIONS ACROSS THE AREA FROM HEAVY RAINS OVER THE PAST SEVERAL
DAYS, FLASH FLOODING IS CONSIDERED LIKELY.

ROTH

ATTN...WFO...BMX...FFC...JAN...LCH...LZK...MOB...SHV...

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

LAT...LON   33488893 33398557 32578488 31858703 31618984 
            31449337 33019332 33349110