MESOSCALE PRECIPITATION DISCUSSION 0149
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
753 AM EDT TUE JUN 24 2014
 
AREAS AFFECTED...NORTHEAST TX, NORTHERN LA, AND CENTRAL MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 241152Z - 241752Z
 
SUMMARY...THUNDERSTORMS WITH HEAVY RAINFALL ARE FORMING INTO A
BAND ACROSS NORTHERN LA AND FAR NORTHEAST TX.  THEY SHOULD EXTEND
INTO CENTRAL MS WITH TIME AND COULD TRAIN FOR A FEW HOURS.  A FEW
LOCALES COULD EXPERIENCE FLASH FLOODING.

DISCUSSION...A FORMING BAND OF THUNDERSTORMS IS DEVELOPING ACROSS
NORTHERN LA JUST AHEAD OF AN OUTFLOW BOUNDARY SET OFF BY
CONVECTION EARLIER THIS MORNING.  CAPES ACROSS LA ARE 1000-2000
J/KG INITIALLY, AND 20-30 KTS OF 0-3 KM SHEAR IS PRESENT ACROSS
THE REGION.  THE 850 HPA AND 700 HPA WINDS SLIGHTLY EXCEED THE
MEAN 850-400 HPA WINDS IN THE REGION AND GENTLY CONVERGE TOWARDS
AN OUTFLOW BOUNDARY ORIGINATING FROM OVERNIGHT CONVECTION, WHICH
IS LEADING TO INCREASED PRECIPITATION EFFICIENCY.  PRECIPITABLE
WATER VALUES ARE 1.75-2" ACROSS THE AREA.  THE INGREDIENTS HAVE
BEEN MET FOR THE WET MULTI-CELL ENVIRONMENT.

BOTH SETS OF CORFIDI VECTORS SUGGEST PROPAGATION OF UNDER 10 KTS,
WITH THE UPWIND CORFIDI VECTORS OPPOSITE THE LOW-LEVEL INFLOW FROM
NORTHEAST LA INTO MS, WHICH COULD CAUSE BACKBUILDING.  THIS BAND
SHOULD DROP SLOWLY EAST-SOUTHEAST WITH TIME AS THE COLD POOL
BECOMES BETTER ESTABLISHED.  CAPES ARE EXPECTED TO INCREASE ACROSS
CENTRAL MS WITH TIME WHERE FLASH FLOOD GUIDANCE VALUES ARE LOWER,
WHICH SHOULD EXTEND THE THREAT TOWARDS THE MS/AL BORDER.  THE
TEMPERATURE GRADIENT ALONG THE RELATED OUTFLOW BOUNDARY SHOULD
ALSO INCREASE WITH DAYTIME HEATING, MAKING IT A MORE EFFECTIVE
SURFACE FOCUS.  HOURLY RAINFALL RATES AS HIGH AS 2.5" AN HOUR ARE
POSSIBLE IN THIS REGION.  WHILE FLASH FLOOD GUIDANCE IS RATHER
HIGH ACROSS LA, THESE COULD BE REACHED WITH A COUPLE HOURS OF
BACKBUILDING AND/OR TRAINING.  A QUICK 2-4" LOCALLY COULD CAUSE A
FEW SPOTS OF FLASH FLOODING WITHIN THE DEFINED AREA.

ROTH

ATTN...WFO...JAN...LIX...LCH...SHV...

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

LAT...LON   32329470 32869179 33238975 33038847 31918887 31369090
            31329344 31849527 32329470