Flash Flood Guidance
Issued by NWS

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000
AWUS01 KWNH 061103
FFGMPD
MNZ000-IAZ000-061501-

MESOSCALE PRECIPITATION DISCUSSION 0312
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
702 AM EDT MON JUL 06 2015

AREAS AFFECTED...PORTIONS OF IA

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

VALID 061101Z - 061501Z

SUMMARY...CLOUD TOPS ARE COOLING WITH DEVELOPING THUNDERSTORM
ACTIVITY ACROSS IA.  WITH HOURLY RAIN RATES UP TO 2.5" POSSIBLE,
FLASH FLOODING IS CONSIDERED POSSIBLE.

DISCUSSION...CONVECTION IS FORMING DOWNWIND OF AN INSTABILITY POOL
ACROSS SOUTHWEST IA, WITH SOME EVIDENCE OF RECENT CLOUD TOP
COOLING ON SATELLITE IMAGERY.  PRECIPITABLE WATER VALUES IN THE
REGION ARE AROUND 2" PER GPS INFORMATION, WHILE VAD WIND PROFILES
INDICATE 25-45 KTS OF 850 HPA INFLOW (2-3 TIMES THE MAGNITUDE OF
THE MEAN 850-400 HPA WIND) INTO A WEAK THERMAL GRADIENT IN CENTRAL
IA.

WHILE MESOSCALE GUIDANCE INDICATES THIS ACTIVITY SHOULD HAVE SOME
LIFE THROUGH 15-16Z AS INSTABILITY AND THE LOW-LEVEL INFLOW FADES.
 HOWEVER, SOME NEW THUNDERSTORMS HAVE FORMED NEAR THE BEST
INSTABILITY, IMPLYING THAT THE AVAILABLE INSTABILITY COULD FADE
QUICKER THAN FORECAST, WITH ORGANIZED HEAVY RAINFALL BEING
POSSIBLE FOR CLOSER TO FOUR HOURS RATHER THAN FIVE.  THIS AREA HAS
BEEN DRY OVER THE PAST WEEK, ALTHOUGH 30 DAY RAINFALL TOTALS IN
THIS REGION HAVE BEEN ON THE ORDER OF 3-6" PER SOUTHERN REGION
ESTIMATES.  WITH HOURLY RAIN RATES ON THE ORDER OF THE THREE HOUR
FLASH FLOOD GUIDANCE POSSIBLE (2.5"), THINK THERE IS SOME THREAT
FOR A MARGINAL FLASH FLOOD EVENT ACROSS CENTRAL AND EASTERN IA.
FORWARD PROPAGATING CONVECTIVE VECTORS ARE QUITE WEAK ACROSS THIS
REGION, IMPLYING A SOUTHWARD DRIFT WHICH COULD LEAD TO SOME
BACKBUILDING WHICH HAS BEEN NOTED ON RECENT RADAR IMAGERY.
MESOSCALE GUIDANCE ADVERTISES LOCAL AMOUNTS OF 2-4" IN THIS REGION
THIS MORNING, WHICH COULD FALL IN A SHORT PERIOD OF TIME.

ROTH

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

ATTN...WFO...ARX...DMX...DVN...MPX...

ATTN...RFC...MBRFC...NCRFC...

LAT...LON   43899219 43029125 41469111 40889192 40739337
            41149481 41959476 42489457 43239418 43789316



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