MESOSCALE PRECIPITATION DISCUSSION 0295
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1117 AM EST SUN DEC 22 2013
 
AREAS AFFECTED...SE LA...SRN MS AND AL...NW FL 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 221616Z - 222116Z
 
SUMMARY...PERSISTENT TRAINING NEAR AN OUTFLOW BOUNDARY MAY YIELD
ISOLATED FLASH FLOODING. THE AXIS OF HEAVY RAIN WILL MOVE ONLY
VERY SLOWLY EAST THIS AFTERNOON.

DISCUSSION...A NARROW SWATH OF 2 TO 4 INCHES OF RAIN HAD FALLEN IN
THE EARLY MORNING HOURS OVER A SMALL PART OF SOUTHERN MS/AL. THIS
AREA FROM JUST NORTH OF GULFPORT MS TO WEST OF THOMASVILLE AL WILL
BE AT SOMEWHAT GREATER RISK OF FLASH FLOODING WITH MODERATE TO
HEAVY RAINS EXPECTED TO CONTINUE. OTHER SURROUNDING
AREAS...TOO...MAY SEE RAINFALL EXCEEDING FLASH FLOOD GUIDANCE ON
THE LONGER...3 TO 6 HOUR...TIME SCALES.

ON THE LARGE SCALE THIS REGION REMAINS WITHIN CONFLUENT 850-700 MB
FLOW WITH PW VALUES OF ABOUT 1.8 INCHES...2.5 STANDARD DEVIATIONS
FROM CLIMATOLOGY...FEEDING IN OFF THE GULF. THE LOW LEVEL JET WILL
BE VEERING AS A SIGNIFICANT SHORTWAVE EXITS TOWARD THE
NORTHEAST...BUT THE RAP AND HRRR MODELS ARE INSISTENT THAT 850-700
MB LIFT REMAINS FOCUSED THROUGH LATE AFTERNOON IN A ZONE FROM SE
LA TOWARD SE AL. WITH SUFFICIENT INFLOW AND WEAK COLD POOL
FORMATION...CONTINUAL REDEVELOPMENT OF CELLS APPEARS LIKELY BEHIND
THE INITIAL OUTFLOW BOUNDARY...WITH CELLS THEN TRAINING FROM SW TO
NE. 

ALTHOUGH THIS TYPE OF ELEVATED CONVECTION IS OFTEN RANDOMLY
DISTRIBUTED...IT MAY BE PERSISTENT ENOUGH TO PRODUCE 3 TO 4 INCHES
OF RAIN LOCALLY THROUGH 21Z...PER NEARLY UNANIMOUS HIGH RESOLUTION
GUIDANCE. THE NARROW ZONE OF FAVORABLE LIFT AND INSTABILITY IS
FORECAST TO DRIFT EAST INTO AL/FL WITH TIME.

BURKE

ATTN...WFO...TAE...BMX...MOB...JAN...LIX...

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

LAT...LON   28859072 29819075 30799012 31828832 32308722 32498612
            32208517 31228478 30008536 28788766 28408992 28859072