MESOSCALE PRECIPITATION DISCUSSION 0003
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1259 AM EST FRI FEB 21 2014
 
AREAS AFFECTED...SOUTHEAST LA...SOUTHERN MS...SOUTHWEST AL 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 210557Z - 210857Z
 
SUMMARY...THUNDERSTORMS CONTINUE TO TRAIN ALONG A PRE-FRONTAL
OUTFLOW BOUNDARY ACROSS PORTIONS OF SOUTHEAST LA...SOUTHERN
MS...AND ARE EXPECTED TO EXTEND INTO SOUTHWEST AL SHORTLY. 
REGIONAL FLASH FLOODING IS POSSIBLE IN THIS AREA.

DISCUSSION...OBSERVATIONS OVER THE LAST FEW HOURS INDICATE THAT AN
OUTFLOW BOUNDARY FROM SOUTHERN MS AND SOUTHEAST LA HAS PUSHED
SOMEWHAT EASTWARD AND IS SLIGHTLY BETTER ALIGNMENT/MORE PARALLEL
TO AN INCOMING COLD FRONT MOVING INTO SOUTHEAST LA AND CENTRAL MS
AT THIS TIME.  PRECIPITABLE WATER VALUES CLOSE TO 1.75" REMAIN IN
THE 99TH PERCENTILE FOR MID TO LATE FEBRUARY, AND LOW-LEVEL INFLOW
FROM THE GULF OF MEXICO OF 50-55 KTS (PER VAD WIND PROFILES)
CONTINUES INTO THE REGION. RESULTANT LOW-LEVEL SHEAR REMAINS IN
THE NEIGHBORHOOD OF 40 KTS, WHICH COMBINED WITH CAPE VALUES ABOVE
1000 J/KG PER THE 01Z RAP GUIDANCE STILL SUPPORTS WET MULTICELLS. 
RADAR ESTIMATES OF RAINFALL ACROSS SOUTHERN MS REMAIN 1-2" PER
HOUR.  DIVERGENCE ALOFT REMAINS SIGNIFICANT NEAR A SPLIT IN THE
UPPER LEVEL JET PATTERN.

CAPES ACROSS THE REGION ARE EXPECTED TO SLOWLY FADE OVERNIGHT. 
WITHIN THE NEXT FEW HOURS, AND COMBINED WITH THE COLD FRONT
OVERTAKING THE OUTFLOW BOUNDARY IN THE NEXT 2-3 HOURS, THE
REGIONAL FLASH FLOOD RISK SHOULD END BY 09Z.  UNTIL THEN HOWEVER,
AREAS OF SOUTHEAST LA, SOUTHERN MS, AND SOUTHWEST AL COULD SEE A
COUPLE HOURS OF CELL TRAINING AS THE OUTFLOW BOUNDARY EXTENDS
FARTHER TO THE EAST AND EAST-NORTHEAST, WHICH COULD LEAD TO
REGIONAL FLASH FLOODING.

ROTH

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

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

LAT...LON   31198768 30588882 30669063 30949000 31538906 32278781
            31198768