MESOSCALE PRECIPITATION DISCUSSION 0012
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
225 PM EDT TUE MAR 10 2015
 
AREAS AFFECTED...ERN LOUISIANA INTO SRN MISSISSIPPI/ALABAMA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 101822Z - 110015Z
 
SUMMARY...A FAVORABLE SETUP FOR TRAINING CONVECTION WITH HOURLY
RATES OF 1-2 IN/HR WILL INCREASE THE THREAT FOR FLASH FLOODING
FROM ERN LOUISIANA INTO SRN MISSISSIPPI AND SWRN ALABAMA THROUGH
00Z. RELATIVELY HIGH FLASH FLOOD GUIDANCE SHOULD LIMIT THE EXTENT
OF FLASH FLOODING BUT LOCALIZED TOTALS OF 4 TO 5 INCHES APPEAR
POSSIBLE.

DISCUSSION...SSWLY FLOW IN THE MID-LEVELS IS EVIDENT ON WATER
VAPOR IMAGERY WITH AN APPROACHING WEAK SHORTWAVE CURRENTLY
CROSSING SOUTH TEXAS. MOISTURE REMAINS ABOVE AVERAGE ACROSS THE
REGION WITH A RELATIVELY NARROW STRETCH OF PRECIPITABLE WATER
VALUES NEAR 1.5 INCHES STRETCHING AHEAD OF A COLD FRONT FROM THE
W-CNTRL GULF COAST TOWARD CNTRL TENNESSEE PER LATEST GPS DATA.
SSWLY FLOW AT 850 MB OF ROUGHLY 30-40 KTS IS IN PLACE VIA VAD WIND
PLOTS AT KLIX TO KDGX...PARALLEL TO THE MEAN STORM MOTIONS. BREAKS
IN CLOUD COVER OVER PARTS OF SRN MISSISSIPPI HAVE HELPED PUSH
SURFACE TEMPS INTO THE MID 70S WHICH IS AIDING IN INSTABILITY OF
NEARLY 500 J/KG. ELEMENTS OF TRAINING HAVE ALREADY BEEN OBSERVED
ON REGIONAL RADAR ACROSS THE THREAT REGION WITH INCREASING
COVERAGE OF CONVECTION JUST SOUTH OF THE LOUISIANA COAST ON IR
IMAGERY.

THE AFOREMENTIONED SHORTWAVE MOVING INTO THE WRN GULF OF MEXICO
SHOULD KEEP FLOW ALOFT NEARLY THE SAME WITH LITTLE ADVANCEMENT OF
THE COLD FRONT THROUGH 00Z NEAR THE GULF COAST. THIS WILL KEEP
UNIDIRECTIONAL SSWLY FLOW IN PLACE WITH PERHAPS A SLIGHT WEAKENING
IN THE 850 MB LAYER WIND SPEEDS PER RECENT RAP/GFS GUIDANCE.
NONETHELESS...A CONSENSUS OF 12Z HI-RES MODEL GUIDANCE SHOWS
SSW-NNE LINES OF HEAVY RAIN FROM NEAR LAKE PONTCHARTRAIN TO THE
CNTRL MS/AL BORDER...LED BY THE 12Z NMM/ARW AND RECENT RUNS OF THE
HRRR WHICH INDICATE 3 HRLY RATES EXCEEDING 3 INCHES THROUGH 00Z.
GIVEN THE MOISTURE AND AVAILABLE INSTABILITY ALREADY IN
PLACE...THESE AMOOUNTS APPEAR LIKELY ON A LOCALIZED BASIS WHICH
COULD CAUSE FLASH FLOODING.

OTTO

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

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

LAT...LON   33048793 32338720 30708827 29948922 29719037 
            30339096 31609028 32838904