Flash Flood Guidance
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000
AWUS01 KWNH 280443
FFGMPD
MNZ000-IAZ000-NEZ000-SDZ000-280842-

MESOSCALE PRECIPITATION DISCUSSION 0405
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1242 AM EDT WED JUN 28 2017

AREAS AFFECTED...SOUTHEAST SD & NORTHWEST IA

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

VALID 280442Z - 280842Z

SUMMARY...THUNDERSTORMS ARE SHOWING TRAINING CHARACTERISTICS IN
SOUTHEAST SD.  HOURLY RAIN RATES TO 2" WITH LOCAL AMOUNTS TO 4"
ARE POSSIBLE.

DISCUSSION...SURFACE OBSERVATIONS AT 04Z REVEAL A MESOSCALE WAVE
ACROSS NORTH-CENTRAL NE.  ELEVATED TO THE NORTHEAST OF THIS
ACTIVITY ARE THUNDERSTORMS WHICH ARE EXPANDING IN COVERAGE ACROSS
SOUTHEAST SD WITH CONSIDERABLY COOLING CLOUD TOPS.  INFLOW AT 850
HPA IS CONVERGENT AT 40-50 KTS, SOMEWHAT EXCEEDING THE MEAN
850-400 HPA WIND.  PRECIPITABLE WATER VALUES ARE 1.25-1.5" PER GPS
DATA.  MUCAPE VALUES IN THE REGION ARE 2000-3000 J/KG.

EXPECTATIONS ARE FOR THE TRAINING CONVECTION TO SHORTEN FROM WEST
TO EAST WITH TIME AS A OUTFLOW BOUNDARY CONTINUES MOVING INTO
EASTERN NE.  THERE IS A CHANCE THAT TRAINING CONVECTION OVER THE
NORTHEAST SIDE OF THE INSTABILITY BUBBLE COULD MOVE INTO NORTHWEST
IA OVER THE NEXT FEW HOURS. FORWARD MOTIONS TO THE EAST TO
EAST-SOUTHEAST AT 20-25 KTS ARE EXPECTED.  THE 00Z GFS COMES THE
CLOSEST TO WHAT IS ONGOING IN THIS REGION -- THE 27/00Z WRF NSSL
ALSO HAD A CLUE HERE WHILE NEWER PIECES OF MESOSCALE GUIDANCE HAVE
FAILED.  HOURLY RAIN RATES TO 2" AND LOCAL AMOUNTS TO 4" ARE
POSSIBLE.  USED A FOUR HOUR HORIZON DUE TO FORECAST UNCERTAINTY.

ROTH

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

ATTN...WFO...DMX...FSD...LBF...OAX...

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

LAT...LON   43669578 43019438 41949436 41719636 42449867
            43379876 43659738


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