NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 242028
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
328 PM CDT Fri Jul 24 2026

.KEY MESSAGES...

- There is a Moderate Swim Risk this afternoon and evening for
  the Lake Michigan breaches in Sheboygan and Ozaukee Counties,
  north of Port Washington. Breaking waves and currents are
  expected. Stay away from dangerous areas like piers,
  breakwalls, and river outlets.

- Warmer and more humid conditions will bring chances for
  thunderstorms at times this weekend into next week.

- There is the potential for severe storms late Saturday night
  through Monday night.

&&

.SHORT TERM...
Issued 328 PM CDT Fri Jul 24 2026

Tonight through Saturday night:

Expect mostly clear skies and light southerly winds until late.
Then low level moisture (with dewpoints in the 60s) will spread
into southwest WI after 3 AM tonight and across the rest of
southern WI through midday. Expect an area of low clouds with
this moisture return which will give us a slower warm-up as
well. Once clouds break up with some low level mixing on
a steady southwest breeze, expect afternoon temps to peak in the
mid 80s.

A mid level shortwave trough crossing the Northern Plains this
afternoon/evening will be the focus for storms. The weakening
storms overnight may hold together as the upper trough gets
into northwest WI and as the low level jet veers eastward. Added
small pops (20%) of showers and storms (although less confident
in lightning).

After the low clouds scatter out (if they do), the elevated
mixed layer (EML) will make its way into WI (probably central).
This will build a capping inversion across southern WI and limit
our storm chances. However, IF the warm air advection and
potential weak shortwave can come together in the late afternoon
toward west central WI, a few thunderstorms could develop and
have the potential for severe levels due to ample
moisture/instability in place and modest shear. This is a highly
conditional scenario, one that is not very likely, but SPC has
the region painted in a Marginal Risk for severe due to this
potential.

At one point, overnight showers/storms looked possible for
portions of central and southern WI late Saturday night into
Sunday morning. These would be triggered by the low level jet,
but that jet is looking like it will be way to far west (per 12Z
models) so that any overnight storms would not reach our area.
However, the GFS (FV3 core) is still trying to produce some
storms in southwest WI early Sunday morning, but this has a
tendency to over-convect.

Cronce

&&

.LONG TERM...
Issued 328 PM CDT Fri Jul 24 2026

Sunday through Friday:

Sunday storms chances remain HIGHLY uncertain. Of course, if any
storms can make it into southern WI Saturday afternoon or night
then the outflow location would set up as a front and help
focus additional storms there. Since Sat storms are pretty
unlikely, then Sunday will be very warm and humid across
southern WI. We are talking about heat indices around 100
(unless clouds hang around). The area will be largely capped,
but a shortwave is expected to cross WI during the late
afternoon and evening. This could be strong enough to trigger
storms on the northern periphery of the cap. Therefore, we are
carrying highest pops (up to 45%) toward central and east
central WI Sunday evening and overnight.

If storms develop just to our north (west central WI) Sunday
afternoon, the storm motion and outflow would usher them
southeastward through southern WI. With our high instability
(greater than 3000 j/kg) and decent shear (40 kt) that is fairly
unidirectional, severe wind is our main threat. However, hail
and a tornado cannot be ruled out.

If the afternoon storms do not develop, then we could see a
round of storms develop on the nose of the low level jet
overnight that is expected to lean into southern WI late. This
would give east central and southeast WI the better chance for
storms late Sun nt into Monday morning (currently carrying 35%
pops). Any outflow from this potential storm complex would be
the focal point for initiation Monday afternoon/evening (may or
may not be in southern WI). These would also have a severe
potential given the warm and humid conditions.

Monday heat currently holds a higher chance to achieve heat
advisory levels (100-104 heat index), but a lot can go wrong
with that if storms or lingering clouds get in the way.

Tuesday and Wednesday, northerly winds help temper our heat and
precip chances. This is due to high pressure building into the
Upper Great Lakes. That central US ridge will push back into
southern WI on Thursday. This will nudge the heat and humidity
back into the area, along with chances for storms.



Cronce

&&

.AVIATION...
Issued 328 PM CDT Fri Jul 24 2026

Look for diurnal cumulus clouds to diminish with sunset this
evening. Winds will be light out of the south overnight. Low
level moisture is going to spread into southwest WI late tonight
and expand into south central WI by mid Saturday morning. A
period of stratus clouds with ceilings of 1500 to 2500 ft is
looking more likely for areas from Madison and westward with
this moisture. The extensive amount of stratus upstream over
western Iowa today lends higher confidence.

There is some indication that MVFR ceilings could make it all t
the way into east central and southeast WI by late morning, but
confidence is too low to put it in the eastern TAF sites at this
time. Ceilings should improve to VFR by the afternoon as
southwesterly winds increase up to around 10 kt and we can mix
out the boundary layer.

Cronce

&&

.MARINE...
Issued 328 PM CDT Fri Jul 24 2026

A brief period of gusty southeast winds toward the nearshore
areas north of Port Washington this afternoon will produce waves
of 3 to 4 feet. A Small Craft Advisory is in effect.

Gusty southerly winds are expected across all of Lake Michigan
through Saturday as a low pressure averaging 29.5 inches
approaches from the northern Plains. A few gusts up to 30 knots
are expected over the north half this afternoon and evening. A
frontal boundary will stall over the Upper Great Lakes, mainly
over Wisconsin and Lake Michigan, through most of Monday. This
will result in increasing thunderstorm chances with severe
storms possible. Very warm, moist and unstable air flowing over
the relatively cool waters may cause patchy marine fog early
next week.

Northerly winds are expected Monday night through Wednesday as
high pressure of 29.9 inches builds over the Upper Great Lakes.
Look for southerly winds and more unsettled weather to resume
Thursday into the next weekend.

Cronce

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643...4 PM Friday to 10 PM Friday.

&&

$$

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