Mesoscale Precipitation Discussion 0771
NWS Weather Prediction Center College Park MD
501 AM EDT Wed Sep 05 2018

Areas affected...Northern Wisconsin into the U.P of Michigan

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

Valid 050900Z - 051300Z

Summary...Continued periods of showers and thunderstorms will
produce 2-3" of rainfall through mid morning. This will occur on
top of already saturated soils, continuing the potential for flash
flooding.

Discussion...An organized area of showers and thunderstorms
evident on regional radar mosaic is continuing to shift northeast
this morning ahead of a vorticity maximum and wave of low pressure
entering SW Wisconsin. Although cloud tops have warmed on the
latest GOES-16 IR imagery, a large area of cool tops coincident
with strongest convection will continue to lift NE through
northern WI and through the U.P. of MI. This is associated with a
500mb vorticity maxima which will eject NE through the morning
continuing the potential for heavy rainfall.

Diffluence aloft continues to drive strong lift as the southern
edge of a 70kt 250mb jet noses into the U.P. This will combine
with PVA ahead of the vorticity max, strong 925-850mb FGEN, and
WAA on a 30-40 kt 850mb LLJ to further enhance omega across the
region. This deep column lift is occurring in an airmass
characterized by PWATs analyzed on the latest RAP to be 1.8 to 2.0
inches which is above record values for the date at APX.

Latest hourly rainfall rates across the U.P. have been around 1 to
1.5 inches per hour according to KMQT WSR-88D, with weaker rain
rates observed across Wisconsin. The rainfall through the next
several hours is not expected to be as extreme as noted upstream
earlier tonight, but high-res guidance has a strong signal for an
additional 2-3" of rainfall. This will occur on top of soils that
have already received significant rainfall earlier tonight, and
may prolong ongoing flash flooding across the area.

Weiss

ATTN...WFO...APX...GRB...MQT...

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

LAT...LON   46738738 46628693 46708613 46718538 46528498
            46218529 45988594 45788671 45578739 45378786
            45238843 45198896 45268953 45468973 45838961
            46138910 46338861 46398830 46608778