Flash Flood Guidance
Issued by NWS

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000
AWUS01 KWNH 260405
FFGMPD
ALZ000-MSZ000-LAZ000-ARZ000-TXZ000-261000-

MESOSCALE PRECIPITATION DISCUSSION 0132
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1204 AM EDT TUE MAY 26 2015

AREAS AFFECTED...ARKLAMISS, EASTERN LA, & SOUTHERN MS

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 260400Z - 261000Z

SUMMARY...A SQUALL LINE IS MOVING INTO AN AREA RECENTLY SATURATED
BY RAINFALL LAST NIGHT.  DESPITE ITS FORWARD PROGRESSION, FLASH
FLOODING SHOULD BE POSSIBLE.

DISCUSSION...A SQUALL LINE IS MOVING SOUTHEAST AT 30+ KT THROUGH
CENTRAL LA AT THIS TIME, WITH 15 KT PROGRESSION SEEN FARTHER
SOUTHWEST ACROSS SOUTHEAST TX.  MUCAPES OF 3000-5000 J/KG LURK
OFFSHORE, WHICH SHOULD FOSTER CONTINUING FORWARD PROGRESSION.
LIKE LAST NIGHT, CONVERGENCE IS SEEN AT 850 HPA ACROSS EASTERN LA
AND MS WITH LOW-LEVEL INFLOW OF 30 KTS PER VAD WIND PROFILES, JUST
ABOVE THE MAGNITUDE OF THE MEAN 850-400 HPA WIND.  PRECIPITABLE
WATER VALUES OF 1.75-2" INHABIT THE REGION.

A FEW OF FACTORS FAVOR A FLASH FLOOD THREAT IN THIS REGION.  SOILS
WERE SATURATED BY MODERATE TO HEAVY RAINFALL LAST NIGHT.  FORWARD
PROPAGATING CORFIDI VECTORS WEAKEN OVERNIGHT, SUGGESTING THAT THE
CONVECTIVE LINE COULD SLOW DOWN ~10 KTS FROM ITS CURRENT MOTION
ACROSS LA AND MS, WHICH COULD RE-ENHANCE RAINFALL RATES.  A FEW
CELLS ALONG THE OUTFLOW BOUNDARY AHEAD OF THE SYSTEM IN SOUTHERN
LA AND SOUTHERN MS HAVE REMAINED STATIONARY.  WITH A SLIGHT UPTICK
OF 850 HPA INFLOW EXPECTED ACROSS SOUTHEAST LA AND MS, MORE
CONVECTION COULD FORM NEAR OR ELEVATED OVER THE OUTFLOW BOUNDARY
BEFORE THE SQUALL LINE COMES THROUGH.  THE AVAILABLE MOISTURE
SUPPORTS RAINFALL RATES UP TO 2" AN HOUR.  THE FLASH FLOOD THREAT
SHOULD SLOWLY ERODE FROM SOUTHWEST TO NORTHEAST ACROSS THIS AREA,
AS 850 HPA INFLOW WEAKENS ACROSS TX AND/OR THE SQUALL LINE
PROGRESSES INTO THE GULF OF MEXICO.  NONE OF MESOSCALE GUIDANCE IS
CARRYING THIS LINE QUICK ENOUGH EASTWARD PER RECENT RADAR TRENDS.
FLASH FLOODING IS A CONCERN OVER SATURATED SOILS, WITH HOURLY RAIN
RATES OF UP TO 2.5" EXPECTED ACROSS TX AND UP TO 2" ELSEWHERE
ACROSS EASTERN LA AND PORTIONS OF MS.

ROTH

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...CRP...EWX...HGX...JAN...LCH...LIX...LZK...MOB...

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

LAT...LON   33649122 32478888 30868841 30228837 30138871
            29838878 29658887 29408919 29258897 29048903
            28858945 29018952 29168957 29198984 29099015
            28949037 29049106 29269142 29399145 29479154
            29489169 29459187 29499275 29669368 29319463
            28699555 28449617 28039697 28819731 29599616
            30129469 31149298 32419229


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