MESOSCALE PRECIPITATION DISCUSSION 0031
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
534 PM EDT MON APR 28 2014
 
AREAS AFFECTED...W-CNTRL MS EXTENDING NEWD INTO SRN TN AND NWRN AL 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 282133Z - 290333Z
 
SUMMARY...THE FLASH FLOOD THREAT ACROSS CNTRL MS INTO NWRN AL AND
SRN TN WILL INCREASE THIS EVENING AS CONVECTION EXPANDS WITHIN A
SLOW MOVING AXIS OF DEEP MOISTURE. TRAINING CELLS ARE EXPECTED TO
CAUSE 2 TO 4 INCHES OF RAIN OVER A 3 HOUR PERIOD AFTER 00Z.

DISCUSSION...SATELLITE/RADAR TRENDS AS OF 21Z INDICATED A SW-NE
ORIENTED SWATH OF CONVECTION EXTENDING FROM CNTRL LA...NEWD INTO
NWRN AL / SRN TN PRODUCING RAINFALL RATES OF 1+ IN/HR WITHIN THE
HEAVIER CORES. THESE CONVECTIVE CELLS ARE OCCURRING WITHIN AN AXIS
OF MODERATE INSTABILITY AND PRECIPITABLE WATER VALUES RANGING
BETWEEN 1.25 AND 1.75 INCHES AHEAD OF A SLOW MOVING COLD FRONT
LOCATED JUST WEST OF THE MISSISSIPPI RIVER AT 21Z.

WHILE THE CONVECTIVE CELLS ARE LARGELY A SEVERE THREAT AT THE
MOMENT...FLASH FLOODING WILL BECOME AN INCREASING THREAT
THROUGHOUT THE REMAINDER OF THE EVENING INTO THE EARLY OVERNIGHT
HOURS AS CELLS CONTINUE TO MERGE AND DEEP MOISTURE NEAR THE GULF
COAST CONTINUES TO FEED INTO THE REGION VIA 850-700 MB FLOW OF
ROUGHLY 50 KTS PER LATEST RAP MODEL FORECAST. THE
ORIENTATION/MAGNITUDE OF THE CLOUD BEARING LAYER MEAN WIND AND LOW
LEVEL INFLOW FROM THE SOUTHWEST WILL BE LARGELY PARALLEL UNTIL THE
COLD FRONT APPROACHES FROM THE WEST...SHUNTING THE DEEPER MOISTURE
OFF TO THE EAST. THIS IS EXPECTED TO ALLOW TRAINING CONVECTION
THROUGH THE REMAINDER OF THE EVENING...APPROACHING CURRENT FLASH
FLOOD GUIDANCE VALUES OF 2-3 IN / 3HR. THIS ARGUMENT IS SUPPORTED
BY RECENT RUNS OF THE HRRR...HRW NMM/ARW...NSSL WRF...ALTHOUGH
THESE MODELS DIFFER ON THE EXACT PLACEMENT OF THE HEAVIEST
RAINFALL.


OTTO

ATTN...WFO...OHX...BMX...HUN...MEG...JAN...

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

LAT...LON   31869130 32569123 34188879 35798666 35788609 34858608
            32958759 31928987 31869130