Flash Flood Guidance
Issued by NWS

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000
AWUS01 KWNH 240612
FFGMPD
TXZ000-OKZ000-241210-

MESOSCALE PRECIPITATION DISCUSSION 0390
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
211 AM EDT SAT JUN 24 2017

AREAS AFFECTED...SOUTHWEST OK & PORTIONS OF NORTHERN TX

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

VALID 240610Z - 241210Z

SUMMARY...ELEVATED CONVECTION CONTINUES TO BUILD AND EXPAND IN
COVERAGE ACROSS THE TX PANHANDLE AND SOUTHWEST OK.  HOURLY RAIN
RATES TO 2" AND LOCAL AMOUNTS TO 4" ARE EXPECTED.

DISCUSSION...SHOWERS AND THUNDERSTORMS HAVE BEEN FORMING ON THE
NORTHWEST SIDE OF AN INSTABILITY POOL CENTERED SOUTH OF DALLAS,
WELL TO THE NORTH OF ASSOCIATED SURFACE BOUNDARIES.  THE
CONVECTION APPEARS TO BE TAPPING INSTABILITY AT THE 700 HPA LEVEL
WHERE THE FLOW IS MORE WESTERLY.  MUCAPE VALUES IN THE AREA ARE
1000-2000 J/KG.  CLOSER TO DALLAS TX, THUNDERSTORMS CONTINUE TO
PROPAGATE SOUTHWEST SLOWLY DUE TO A LONG-LIVED OUTFLOW
BOUNDARY/CONVECTIVE ARC WHICH WAS SPAWNED BY THUNDERSTORM ACTIVITY
IN IA AND CO 24 HOURS AGO.  PRECIPITABLE WATER VALUES OF 1.5-2"
EXIST HERE PER GPS DATA.  EFFECTIVE BULK SHEAR OF 25-50 KTS IS
HELPING TO ORGANIZE THUNDERSTORMS.  THE MEAN 850-400 HPA WINDS ARE
FAIRLY LIGHT THROUGHOUT THE REGION, WHICH COULD MAGNIFY RAINFALL
EFFICIENCY.

HOURLY RAIN RATES UP TO 2" ARE EXPECTED.  MASS FIELD-WISE, A
MESOSCALE WAVE IS EXPECTED TO DROP SOUTHWEST WITH TIME INTO
CENTRAL TX DUE TO THE MOBILE OUTFLOW BOUNDARY, WHICH SHOULD ALLOW
CONVECTION FROM NEAR DALLAS TO   THE 00Z NAM CONEST APPEARS TO
HAVE THE BEST HANDLE OF THIS ACTIVITY FROM A PATTERN PERSPECTIVE,
BUT THE GUIDANCE IS UNIFIED ON A SIGNAL FOR ~4" IN THIS AREA.
THERE IS CONCERN, BASED ON THE NAM CONEST, THAT THE ACTIVITY COULD
BRIDGE ACROSS TO THE SOUTHWEST MOVING CONVECTION MOVING ACROSS THE
DALLAS-FORT WORTH AREA AT THIS TIME.  THE EXPECTED LOCAL TOTALS
COULD CHALLENGE THE HIGH FLASH FLOOD GUIDANCE VALUES IN THIS AREA
-- THE THREAT APPEARS HIGHEST IN URBAN LOCATIONS.

ROTH

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

ATTN...WFO...AMA...EWX...FWD...LUB...OUN...SHV...SJT...

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

LAT...LON   35510176 35259782 32849498 31119630 30949796
            31739956 34300167



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