Flash Flood Guidance
Issued by NWS

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000
AWUS01 KWNH 021738
FFGMPD
PAZ000-MDZ000-WVZ000-OHZ000-KYZ000-INZ000-022336-

MESOSCALE PRECIPITATION DISCUSSION 0340
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
137 PM EDT TUE SEP 02 2014

AREAS AFFECTED...PORTIONS OF THE OH VALLEY

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

VALID 021736Z - 022336Z

SUMMARY...AN OUTFLOW BOUNDARY IS EXPECTED TO BE THE FOCUS FOR
RENEWED THUNDERSTORM ACTIVITY OVER THE NEXT SEVERAL HOURS.
RAINFALL RATES UP TO 2" COULD CAUSE FLASH FLOODING.

DISCUSSION...AN OUTFLOW BOUNDARY FROM OVERNIGHT THUNDERSTORM
ACTIVITY UPSTREAM ACROSS THE OHIO VALLEY HAS BEGUN TO LIE
DOWN/STALL ACROSS EASTERN KY, WITH SOME SCATTERED THUNDERSTORMS
STILL EXISTING IN ITS VICINITY ACROSS WV.  OTHER THUNDERSTORMS ARE
MOVING TOWARDS THE WESTERN EDGE OF THIS REGION FROM SOUTHERN IN.
PRECIPITABLE WATER VALUES OF ~1.75" ARE EXPECTED ACROSS THE REGION
THIS AFTERNOON AND EVENING, WHILE 850-700 HPA INFLOW REMAINS CLOSE
TO 30 KTS, SIMILAR TO THE MAGNITUDE OF THE 850-400 HPA MEAN
LAYERED WIND.  REGIONAL SOUNDINGS SHOW SATURATED LOW-LEVELS AND
REVEAL UNIDIRECTIONAL FLOW WITH HEIGHT WITHIN THE TROPOSPHERE.
MIXED LAYER CAPES ARE IN THE 1000-2000 J/KG RANGE, AND SHOULD
BUILD FURTHER BEFORE CONVECTION BREAKS OUT ACROSS THE REGION.  THE
THRESHOLD FOR THE WET MULTICELL ENVIRONMENT HAS BEEN REACHED.

THE 06Z SSEO NEIGHBORHOOD PROBABILITIES OF EXCEEDING THREE HOURLY
FLASH FLOOD GUIDANCE VALUES ARE >50% ACROSS PORTIONS OF EASTERN
KY, WV, AND SOUTHWEST PA AND THAT THE THREAT FOR HEAVY RAINFALL
COULD PERSIST AS LATE AS 02Z.  THE MOST RECENT MESOSCALE GUIDANCE
SHOWS LOCAL 2" AMOUNTS POSSIBLE IN THIS REGION.  RECENT THOUGHTS
FROM SPC INDICATE THAT WV STANDS A GOOD CHANCE OF SEEING REPEAT
CONVECTION THIS AFTERNOON AND EVENING.  WITH THE MOISTURE PRESENT,
HOURLY RAINFALL RATES UP TO 2" ARE POSSIBLE.  CONVECTION IS
EXPECTED TO BE ON THE MOVE, BUT RANDOM CONVECTIVE CELLS/LINE
SEGMENTS COULD TRAIN GIVEN THE UNIDIRECTIONAL FLOW PRESENT.  FLASH
FLOODING IS POSSIBLE, PARTICULARLY IN AREAS SATURATED BY RECENT
RAINS.

ROTH

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

ATTN...WFO...CTP...ILN...JKL...LMK...PBZ...RLX...RNK...

ATTN...RFC...OHRFC...

LAT...LON   41177993 40737921 39697941 39597942 38247998
            37678119 37548297 37888417 38558489 39108481
            39528303 40028190 40698068


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