NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 160043
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
743 PM CDT Mon Jun 15 2026

.KEY MESSAGES...

- Showers (60-90 percent chance) and scattered thunderstorms on
  Tuesday. Small hail expected with the thunderstorms.

- Widespread showers (80-90 percent chance) and scattered
  thunderstorms Wednesday and Wednesday night. Heavy rain and a
  conditional threat for severe thunderstorms is forecast.

- Winds and waves may approach Small Craft Advisory criteria
  Wednesday afternoon into Thursday.

- Next chances for thunderstorms develop Saturday and Sunday.

&&

.UPDATE...
Issued 740 PM CDT Mon Jun 15 2026

No major changes to the going forecast. 18z guidance still
resolves the LLJ southeast of the MN shortwave trough producing
some widely scattered showers (or even weak thunderstorms) late
tonight into early Tuesday morning. The intensity of that narrow
LLJ increased just a bit, leading to wind shear being added to 3
of our TAF sites (KMSN, KUES, and KJVL).

The 18z guidance also depicts the aforementioned afternoon
redevelopment, with some scattered showers expected and chances
for thunderstorms, some of which could easily produce small hail
given the low freezing levels for this time of year.

Sheppard

&&

.SHORT TERM...
Issued 314 PM CDT Mon Jun 15 2026

Tonight through Wednesday Night:

Quiet weather will linger into this evening as high pressure
continues to shift east overnight. During the pre-dawn hours on
Tuesday, a compact shortwave is expected to move in from central
Minnesota, bringing ~15 to 30% chances for light rain showers.
There should be a bit of a lull in shower activity late Tuesday
morning as early morning rain activity dissipates/pushes east
and the shortwave closes into a compact upper low over NE
Wisconsin. However, scattered shower and tstorm development is
expected to increase Tuesday afternoon as daytime heating
promotes steepening lapse rates in the low to mid levels. CAPE
will be weak, only reaching 500 to 1000 J/kg amid weak effective
shear of 15 knots. Storms will be poorly organized, but
relatively low freezing levels may promote small hail for any
stronger updraft, especially over southeast Wisconsin where
there will be better opportunity for instability to build.

The wave will quickly move east and deamplify Tuesday night.
Another larger trough is expected to rotate southeast out of
the Northern Plains Wednesday morning and amplify through
midday, increasing the upper level flow over the Corn Belt. The
effects of the upper low will drive divergence aloft Wednesday
morning and a large complex of storms is expected to become
organized over northeast Iowa around 7am Wednesday. This complex
of storms is then expected to continue ESE through the morning,
barely grazing southern WI as it heads into Indiana.

Behind this morning complex, a surface warm front is expected
to surge northward, driven by surface WAA ahead of an occluding
low pressure center over the northern MS Valley. The position of
this front will greatly determine where Wednesday afternoon's
severe weather risk will occur. Some CAMs suggest the front will
stay south of the WI/IL border, confining a severe risk to IL,
while some show the warm front crossing into Wisconsin's
southern row of counties. IF the warm front indeed does make it
into southern WI, an all hazards severe risk would be possible
along and south of the warm front Wednesday late afternoon and
early evening as storms may latch onto the front itself. Given
the disagreement among the CAMs, model trends will have to be
watched over the next two days for a definitive forecast.

CMiller

&&

.LONG TERM...
Issued 243 PM CDT Mon Jun 15 2026

A surface low pressure system is expected to move east toward
Michigan Thursday morning, bringing a slight chance for
precipitation in southeast WI (10-20%). Cold air advection will
continue as a shortwave trough moving in from the northwest will
intensify over the region Thursday afternoon. High temperatures
are expected to be in the low 70s with dewpoints in the low 50s.

A region of high pressure is expected to build over the Plains
Thursday night into Friday, but PW values of 0.7-0.9" and higher
relative humidity values Friday morning could bring the potential
for showers, although the chance remains low. Precipitation
chances increase into Saturday (20-40%) as the high pressure
systems moves off the Plains into the lower Mississippi River
Valley. This chance increases further for Sunday (20-50%) as a
cold front and a low pressure system move from the northwest into
southern WI.

Monday's chances for precipitation decrease from Sunday as a
shortwave ridge enters the region and the low pressure system sits
south of WI.

Zawlocki

&&

.AVIATION...
Issued 700 PM CDT Mon Jun 15 2026

VFR and quiet weather continue through the rest of this evening,
with the FEW/SCT cumulus clouds eroding and lingering SCT
(briefly BKN) higher altitude clouds over 20,000 ft. Surface
winds decelerate and turn SW. As a shortwave trough sags
southeastward from MN into WI, a narrow WSW LLJ is expected to
produce 35-40kt winds at the 2,000ft level late tonight over
portions of southern WI, yielding a brief window of LLWS
(included in the KMSN, KUES, and KJVL TAFs). This same feature
may kick-start some widely scattered showers or even weak
thunderstorms, with PROB30 groups late tonight into early
Tuesday morning included in the TAFs as it passes. VFR ceilings
expected with this activity.

The aforementioned shortwave trough continues it's progression
into southern WI (our region) Tuesday afternoon, with scattered
showers expected and a chance for thunderstorms. These storms
are generally expected to be sub-severe, but could easily
produce small hail (due to the cold air aloft). Generally VFR
ceiling altitudes with this activity, but cannot rule out some
brief MVFR ceilings. Visibility may drop to MVFR (or even
briefly IFR) with the heaviest showers / storms.

Sheppard

&&

.MARINE...
Issued 241 PM CDT Mon Jun 15 2026

Southwesterly winds shift southerly into early Tuesday as a low
pressure system deepens over northern Lake Michigan (29.65
inches), shifting eastward over the northern half of the lake
Wednesday morning, with winds becoming northwesterly Wednesday.
Scattered showers and storms over central and southern Lake
Michigan Tuesday night through Wednesday.

Following the chance for precipitation, a low pressure system will
move over Lake Michigan Thursday morning (29.47 inches), causing a
wind shift from southeasterly Wednesday night to northwesterly
Thursday morning, with the potential for breezy conditions.

A high pressure system will move in Friday, creating continued
breezy, westerly winds, primarily over the southern half of Lake
Michigan.

Zawlocki

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

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