NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 250435
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1135 PM CDT Mon Aug 24 2026

.KEY MESSAGES...

- High swimming risk at Sheboygan County beaches Tuesday
  afternoon and evening.

- Scattered showers & storms (~30-50% chances) possible Tuesday night
  areawide & once more Wednesday across the east. Can't rule
  out an isolated storm with gusty winds or hail.

- Rain-free & pleasant conditions late week.

- Trending active this weekend into early next week, with
  multiple periods of showers and storms forecast.

&&

.SHORT TERM...
Issued 1135 PM CDT Mon Aug 24 2026

Tonight through Wednesday:

With high pressure slowly moving east out of Wisconsin tonight,
dry weather, clear skies and light winds are expected. There is
a small chance again for some fog to develop overnight into
early Tuesday morning. The potential for fog to develop is very
limited in scope to low lying areas and river valleys,
especially the Wisconsin River Valleys. Those same areas that
got patchy fog to develop last night will be the ones at risk
again tonight. Any fog that does develop will dissipate shortly
after sunrise.

The influence of the high pressure will linger a bit through
Tuesday afternoon then a low pressure system in southern Canada
will approach the northern Great Lakes Region passing Lake
Superior Tuesday night into Wednesday. As this low approaches
the pressure gradient will tighten a bit which will result in
some breezy south winds over Lake Michigan. This is expected to
build waves across portions of the western nearshore zones. Thus
a Small Craft Advisory and Beach Hazard statement is in effect
for areas north of Port Washington. Steer clear of the water
for those areas Tuesday afternoon and evening.

Heading into Tuesday night through Wednesday afternoon, rain and
storm chances will increase. Rain/storm chances are around 30-50
% at its peak early Wednesday morning. Rain chances look to hold
off until around midnight or there after for all of southern
Wisconsin. Available moisture will be good and shear is
expected to be around 20-30 kts through Wednesday afternoon.
Instability will be the one ingredient to keep an eye on through
the overnight hours for any stronger storms. The NAM soundings
seem to be the most aggressive with instability, particularly
MUCAPE, during the overnight hours. However, there is some
pessimism on if this is being overdone. Not just by the NAM but
other guidance as well. Lightning by far will be the biggest
hazard during the overnight hours. At this point, can't rule out
an isolated stronger storm, but confidence on that is very
low. If a storm does become more organized a brief gusty winds
or small hail would be the main concerns. For what its worth it
looks far more likely that isolated to scattered weak thunderstorms
and rain will be all we get.

Rain and storm chances will linger through Wednesday afternoon
until the cold front moves through the area. Some guidance
suggests storms redeveloping along the cold front for eastern
counties during the afternoon hours. In the wake of the early
morning activity this would by far be the better window for an
isolated strong to severe storm. Instability will be good from
diurnal heating, forcing from the cold front and linger PVA
aloft from the exiting low. The guidance that is the most robust
with these storms does have the cold front moving through a bit
slower than others so the timing of the front will be the big
thing to watch here. But if strong storms do develop then gusty
winds and hail will be the primary concerns.

Patterson

&&

.LONG TERM...
Issued 1135 PM CDT Mon Aug 24 2026

Wednesday night through Sunday:

As the low pressure system moves east into Quebec, high pressure
is expected to move down from the Northern Plains and Canada
into the Great Lakes Region. High pressure is expected to have
influence across Wisconsin from roughly Wednesday night through
Friday bringing dry weather, light winds and pleasant near
normal temperatures.

Heading into the weekend, aloft (around 500 mb) zonal flow
looks to return as the ridge flattens out. This will place the
Great Lakes Region back into a regime of shortwave troughs
moving through the flow with multiple chances for rain and
storms. Rain and storms chances are expected to increase as
early as Saturday night with additional person of storms
looking to continue through Monday. Ahead of the first shortwave
trough late Saturday, winds are expected to shift to the south
to southwest which will allow for some decent WAA. The moisture
return should be enough to help support rain with any lift we
get aloft. Global models are also still showing the LLJ moving
into Wisconsin which could further support storm development at
times. At the end of the day, a lot  of the storm chances are
going to be controlled by some mesoscale parameters that are
just a bit to early have specifics on timing or exact location
of rain/storms. What we do know is that, PWATS will be good
around 1.5 to 2 inches which will promote heavy rain chances.
Instability will be good at times, especially with the presence
of the LLJ at times, and shear looks to be decent as well. So
there is support at the base level for ingredients for strong to
severe storms. However, do all of these ingredients line up at
the appropriate times. That will still need to be hashed out.
For planning purposes, this is not expected to be a washout on
any given day. There will likely be many breaks or lulls between
rounds of rain. So keep up to on the forecast.

Patterson

&&

.AVIATION...
Issued 1135 PM CDT Mon Aug 24 2026

Largely VFR conditions are expected through Tuesday evening.
Under the clear skies and light winds tonight, there will again
be a chance for patchy fog to develop tonight for low lying
areas and river valleys. The typical terminals in low lying
areas ie:LNR & JVL are the most likely to be impacted. If fog
develops visibilities could fall to 2-4 SM. Any fog that does
develop will burn off after sunrise. Light southwest winds
develop late Tuesday afternoon. As winds turn to southwesterly,
mid to high level clouds will begin to stream in from the west.
Heading into Tuesday night, rain chances will increase from west
to east. The best chances for rain look to hold off until after
midnight (06Z). Lower visibilities to around 4-6 SM and
ceilings around 4-6 kft will be possible with any storms. Rain
and storm chances are expected to linger into late Wednesday
afternoon, especially across eastern Wisconsin. As rain comes to
an end winds will shift to northwesterly.

Patterson

&&

.MARINE...
Issued 1135 PM CDT Mon Aug 24 2026

Low pressure around 29.7 inches in western Quebec will slow move
northeast tonight into Tuesday morning. While this low pressure
moves away so too will the high pressure around 30.1 inches
centered over Wisconsin this evening. Winds will diminish as this
high pressure moves east becoming light and variable tonight. As
the high shifts east into Michigan, light south to southwest winds
are expected across the lake.

Heading into Tuesday evening, a low pressure system around 29.7
inches from the northern Plains will move eastward toward Lake
Superior. Southerly wind across the lake are expected to become
breezy Tuesday afternoon and evening, which will result in
building waves across central and northern portions of the
Lake. Small Craft conditions are expected in nearshore zones
during a brief window from roughly 4-10 PM north of Port
Washington. As the low continues east, an associated cold front
will move across Lake Michigan shift winds to the northwest late
Wednesday afternoon/evening. Breezy northwest winds are
expected through Wednesday night. Showers and thunderstorms will
accompany the approaching/passing surface low and cold front.
An isolated stronger storm with hail and gusty winds will be
possible but chances are low. High pressure around 30.1 inches
will gradually build in from the Northern Plains behind this
exiting low for Thursday and Friday. Light north to northeast
winds are expected.

Patterson

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052...4 PM Tuesday to 10 PM
     Tuesday.

LM...Small Craft Advisory...LMZ643...4 PM Tuesday to 10 PM Tuesday.

&&

$$

Visit us at weather.gov/milwaukee

Follow us on Facebook, X, and YouTube at:
www.facebook.com/NWSMilwaukee
www.x.com/NWSMilwaukee
www.youtube.com/NWSMilwaukee