987
AWUS01 KWNH 160731
FFGMPD
WIZ000-ILZ000-MNZ000-IAZ000-161320-

Mesoscale Precipitation Discussion 0446
NWS Weather Prediction Center College Park MD
330 AM EDT Sun Jun 16 2024

Areas affected...IA into southeastern MN/western WI, far
northwestern IL

Concerning...Heavy rainfall...Flash flooding possible

Valid 160729Z - 161320Z

Summary...Localized flash flooding will remain possible for
portions of the Upper Mississippi Valley through 13Z. Training of
heavy rain may allow for rainfall rates as high as 3 in/hr but 1-2
in/hr rates should be most common. Additional rainfall of 2-4
inches is expected over the next 6 hours, but with much of that
falling within a 3 hour period or less.

Discussion...A combination of satellite and radar imagery showed
two primary MCVs over the Upper Mississippi Valley with active
areas of showers and thunderstorms nearby as of 07Z. The first was
over IA, roughly 70 miles northeast of DSM, with slower moving and
a few repeating cells to the west of the MCV. The second MCV was
over western WI, about 70 miles east-northeast of MSP while a
third, smaller MCV, was identified about 10 miles northwest of
MSP. Recent thunderstorm development was noted over southern
MN...between the MCV centers...within a strong warm advection
pattern, where 40 to 50+ kt south-southwesterly 850 mb winds were
overrunning a pair of warm fronts as depicted on the 06Z WPC
surface analysis. SPC mesoanalysis data showed precipitable water
values of 1.6 to 1.8 inches across the region (near the
climatological max PW for mid-June at MPX) and MUCAPE of ~500 to
1000 J/kg. However, instability weakened with northeastern extent
into WI, limiting rainfall intensity east of the Mississippi River.

A general northeastward motion is expected with the MCVs over the
next 3-6 hours and continued warm advection with 850 mb jet speeds
peaking near 50 kt from the western half of IA into southeastern
MN is forecast by the RAP through 12Z. Some increase in
instability is anticipated toward the northeast with continued low
level moisture transport, and given the anomalous moisture present
and modest upper level diffluence over the region, maintenance of
localized heavy rain is expected through the morning. Where cells
align within the steering flow, training will allow for rainfall
rates of 1-2 in/hr, but localized rates near 3 in/hr cannot be
ruled out. An additional but localized 2-4 inches of rain is
expected across portions of the Upper Mississippi Valley through
13Z which may result in flash flooding.

Otto

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...ARX...DLH...DMX...DVN...GRB...LOT...MKX...MPX...

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

LAT...LON   46069261 46049062 45019007 43758965 42838926
            41988927 41498998 41359139 41479340 41999492
            43289487 44509445