Flash Flood Guidance
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000
AWUS01 KWNH 270324
FFGMPD
LAZ000-TXZ000-270923-

MESOSCALE PRECIPITATION DISCUSSION 0137
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1124 PM EDT TUE MAY 26 2015

AREAS AFFECTED...PORTIONS OF EASTERN TX/WESTERN LA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 270323Z - 270923Z

SUMMARY...A BROAD EAST-WEST BAND OF THUNDERSTORMS HAS FORMED WHICH
HAS BEEN UNLEASHING HEAVY RAINFALL UPON NORTH-CENTRAL TX.  FLASH
FLOODING IS CONSIDERED LIKELY OVER SATURATED SOILS.

DISCUSSION...A BAND OF THUNDERSTORMS CONTINUES TO GROW UPSCALE --
WITH COOLING CLOUD TOPS -- ACROSS NORTH-CENTRAL AND NORTHEAST TX,
FED BY 25-30 KT INFLOW AT 850 HPA OVERRIDING AN OUTFLOW
BOUNDARY/FORMING COLD POOL, MIXED LAYER CAPES OF 3000-4000 J/KG,
AND PRECIPITABLE WATER VALUES OF ~1.4".  SOME BACKBUILDING HAS
BEEN SEEN TOWARDS A PAIR OF MESOSCALE WAVES ON THE BOUNDARY ACROSS
NORTH-CENTRAL AND NORTHEAST TX.  CELL MOTION HAS BEEN ROUGHLY
EAST-SOUTHEAST AT 25 KTS, CLOSE IN MAGNITUDE AND DIRECTION TO THE
FORWARD PROPAGATING CORFIDI VECTORS AND 1000-500 HPA THICKNESS
PATTERN IN THE REGION.

WHILE THE MESOSCALE GUIDANCE HAS A SIGNAL FOR LOCAL 2-4" OF RAIN
IN THIS REGION, THE CURRENT LOCATION AND BREADTH OF THE
THUNDERSTORM BAND HAS EXCEEDED ALL MODEL EXPECTATIONS.  RECENT RAP
FORECASTS INDICATE STEADY STATE 850 HPA INFLOW OVERNIGHT, WHICH
SHOULD ALLOW THE CONVECTION TO CONTINUE TO INTENSIFY AS IT
CONTINUES MOVING EAST-SOUTHEAST.  CELL TRAINING/MERGERS ARE THE
MAIN CONCERN HERE.  WHILE HOURLY RAIN RATES HAVE RECENTLY NEARED
3" PER RADAR ESTIMATES, ONCE THE COMPLEX STARTS TO FORWARD
PROPAGATE, RAIN RATES OF UP TO 2" CAN BE GENERALLY EXPECTED.  MUCH
OF THIS AREA JUST RAINED HEAVILY YESTERDAY, SO SOILS ARE
SATURATED.  FLASH FLOODING SHOULD CONTINUE TO OCCUR IN THIS REGION.

ROTH

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

ATTN...WFO...FWD...HGX...LCH...SHV...SJT...

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

LAT...LON   33049566 32629376 31219330 30779400 30919590
            31199737 31309786 31869939 32419979 32839897



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