Flash Flood Guidance
Issued by NWS

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000
AWUS01 KWNH 241410
FFGMPD
TXZ000-241800-

MESOSCALE PRECIPITATION DISCUSSION 0393
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1009 AM EDT SAT JUN 24 2017

AREAS AFFECTED...SOUTHEAST TX

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

VALID 241400Z - 241800Z

SUMMARY...VERY SLOW-MOVING SHOWERS AND THUNDERSTORMS WITH INTENSE
RAINFALL RATES MAY CAUSE SOME ADDITIONAL CONCERNS FOR RUNOFF AND
POSSIBLE FLASH FLOODING OVER THE NEXT FEW HOURS.

DISCUSSION...EXPERIMENTAL GOES-16 0.64 MICRON/VIS IMAGERY SHOWS AN
AGITATED CU/TCU FIELD ALONG THE IMMEDIATE MIDDLE AND UPPER TX
COAST...WITH NUMEROUS SMALL SCALE CLOUD STREETS ADVANCING
NORTHWEST IN CONJUNCTION WITH THE LOW LEVEL SOUTHEAST FLOW. THE
BOUNDARY LAYER IS RATHER UNSTABLE AND THE INTERACTION OF THIS WITH
AN OUTFLOW BOUNDARY A BIT FARTHER INLAND COUPLED WITH A VERY
DIFFLUENT UPPER AIR SIGNATURE IS ALLOWING CONVECTION TO EXPAND IN
COVERAGE.

CONVECTIVE CELL MOTION IS QUITE WEAK THOUGH WHICH IS ALLOW FOR
SOME HEAVY RAINFALL TOTALS. ALREADY THERE HAVE BEEN LOCALLY SOME 3
TO 4+ INCH AMOUNTS AROUND THE HOUSTON METROPOLITAN AREA...WHICH IS
BEING AIDED BY A VERY MOIST ENVIRONMENT WITH PWATS UP BETWEEN 2 TO
2.2 INCHES. THIS IS ENHANCING THE RAINFALL RATES WITH HIGHLY
EFFICIENT RAINFALL PROCESSES AT WORK.

EXPECT SOME ADDITIONAL RAINFALL AMOUNTS OF AS MUCH AS 2 TO 4
INCHES...WITH ISOLATED TOTALS POSSIBLE AS HIGH AS 6 INCHES WHERE A
FEW CELL MERGERS OCCUR AND TEND TO STALL GIVEN THE WEAK STEERING
FLOW/CELL MOTION.

ORRISON

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

ATTN...WFO...CRP...EWX...HGX...LCH...

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

LAT...LON   30389484 30259401 29799399 29589469 29369507
            29069574 28809635 28739694 28839736 29109756
            29529739 29979649 30339564



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