Flash Flood Guidance
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000
AWUS01 KWNH 250524
FFGMPD
TNZ000-ALZ000-MSZ000-LAZ000-ARZ000-251123-

MESOSCALE PRECIPITATION DISCUSSION 0124
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
124 AM EDT MON MAY 25 2015

AREAS AFFECTED...MS & ADJACENT AREAS OF LA, AL, AND TN

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

VALID 250523Z - 251123Z

SUMMARY...THUNDERSTORMS WITH HOURLY RAIN RATES UP TO 2" COULD
CAUSE FLASH FLOODING ACROSS THE REGION.

DISCUSSION...SEVERAL HEAVY RAIN CORES DURING THE PAST COUPLE HOURS
HAVE LED TO 1.5-2" AN HOUR RAIN RATES ACROSS CENTRAL MS AND
WESTERN TN.  THUNDERSTORMS HAVE FORMED IN NORTH-SOUTH BANDS TO THE
NORTH OF A WEAK THERMAL BOUNDARY LOCATED IN SOUTHEAST LA, SOUTHERN
MS, AND SOUTHERN AL WITHIN AN AREA OF BROAD CONVERGENCE AT 850
HPA.  WHILE INSTABILITY ACROSS THE REGION HAD BEEN DECREASING,
RECENT SPC MESOANALYSES INDICATE AN UPTICK TO MUCAPES ACROSS THE
AREA, WHICH HAS BEEN MATCHED ON THE MOST RECENT RAP RUN.

MOST OF THE MESOSCALE GUIDANCE SHOWS 2-3" LOCAL MAXIMA IN THIS
REGION, NEAR THE THREE HOURLY FLASH FLOOD GUIDANCE VALUES.  THE
NOTABLE EXCEPTION IS THE 00Z CANADIAN REGIONAL MODEL, WHICH
INDICATES LOCAL AMOUNTS OF 5"+ ARE POSSIBLE INTO THE MORNING
HOURS.  RAINFALL EFFICIENCY IS BEING FOSTERED BY PRECIPITABLE
WATER VALUES OF 1.75-2", 850 HPA INFLOW OF 25-40 KTS WHICH
SLIGHTLY EXCEEDS THE MEAN 850-400 HPA WIND, AND MUCAPE VALUES IN
EXCESS OF 1000 J/KG ACROSS SOUTHERN MS WHICH ARE EXPECTED TO CREEP
NORTHWARD INTO CENTRAL MS WITH TIME.  SAB/NESDIS MENTIONED THAT AN
OUTFLOW BOUNDARY FROM FL CONVECTION EARLIER TODAY MIGHT CONTRIBUTE
TO ISSUES ACROSS SOUTHERN AL OVER THE NEXT SEVERAL HOURS.
POSSIBLE WORDING WAS USED OVER LIKELY AS COVERAGE OF THE HEAVY
RAINFALL WITHIN THIS REGION MIGHT BE LESS THAN USUALLY SEEN IN AN
MPD.  HOURLY RAIN RATES UP TO 2" COULD CAUSE FLASH FLOODING.

ROTH

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

ATTN...WFO...BMX...HUN...JAN...LCH...LIX...MEG...MOB...OHX...

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

LAT...LON   36408833 35838787 33458795 31418779 30228754
            30118861 29808873 29388911 29128891 28958913
            28848943 28918946 29128952 29228984 29089012
            28999065 29059093 29279134 29589124 30089100
            31079118 33119088 34919024 36108939


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