Flash Flood Guidance
Issued by NWS

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000
AWUS01 KWNH 210226
FFGMPD
WIZ000-210600-

MESOSCALE PRECIPITATION DISCUSSION 0817
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1025 PM EDT WED SEP 20 2017

AREAS AFFECTED...EASTERN WISCONSIN

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

VALID 210230Z - 210600Z

SUMMARY...EFFICIENT RAINFALL PROCESSES REMAIN AS CONVECTION MOVES
SLOWLY ACROSS E WI CONTINUING POSSIBLE FLASH FLOODING CONDITIONS
FOR THE NEXT FEW HOURS.

DISCUSSION...GOES-16 10.3UM CLEAR IR CHANNEL DEPICTS A MATURE MCS
ACROSS EAST CENTRAL WI WITH NUMEROUS PERCOLATING OVERSHOOTING TOPS
INDICATIVE OF THE REMAINING INSTABILITY.  RAP ANALYSIS SHOWS
SUFFICIENT 2000 J/KG MUCAPES AND A NARROW BUT HIGH MOISTURE
GRADIENT ALONG AND JUST E OF THE FRONTAL BOUNDARY.  CIRA LAYERED
PW SHOW THIS MOISTURE IS FAIRLY DEEP THROUGH THE BULK OF THE
ATMOSPHERE LEADING TO TOTAL VALUES NEAR 2.0".  WHILE LOW LEVEL
INFLOW HAS VEERED SLIGHTLY TO BECOME MORE PARALLEL TO THE
ORIENTATION OF THE FRONT/CONVECTIVE LINE(S)...THERE IS SUFFICIENT
FLUX TO SUPPORT EFFICIENT RAINFALL PROCESSES.  RECENT
REPORTS/RADAR MOSAIC SUPPORT RAINFALL RATES IN EXCESS OF 2"/HR.

RAP 500-1000MB THICKNESS FIELD SHOWS A HIGHLY AMPLIFIED RIDGE IN
SE WI WHILE MEAN 400-850MB 20-25KT MEAN FLOW THAT WOULD SUPPORT
SOME SLOW SELY DRIFT AS PROPAGATION VECTORS ARE ABOUT 5KTS.  THIS
COMBINED WITH THE RAINFALL RATES ARE SUGGESTIVE OF TOTALS OF 2-3"
WITH POSSIBLE ISOLATED 4" CONTINUING THE ISOLATED THREAT FOR FLASH
FLOODING PARTICULARLY FURTHER NORTH ACROSS CENTRAL E WI WHERE
MULTIPLE LINES WILL TRACK THROUGH THE SAME AREAS IN FAIRLY QUICK
SUCCESSION.

GALLINA

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

ATTN...WFO...GRB...MKX...

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

LAT...LON   44518751 43938750 43318774 42888767 42688797
            42678850 42798913 43118957 43668912 44408826



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