NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 211040
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
540 AM CDT Sun Jun 21 2026

.KEY MESSAGES...

- Rain is looking likely from Madison to Milwaukee and south to
  the IL border for this afternoon and evening. Around one half
  inch of rain is expected south of the I-94 corridor.

- Moderate to high swim risk expected for Lake Michigan beaches
  Monday. Keep out of the water and away from dangerous areas
  like piers and breakwalls!

- On and off thunderstorm chances Tuesday through Thursday, and
  potentially again next weekend.

- Below normal temps continue.

&&

.UPDATE...
Issued 540 AM CDT Sun Jun 21 2026

06z interim model guidance indicates the forecast remains on
track. It is tough to say exactly where the rainy / dry weather
cutoff point will setup (north to south) this afternoon and
evening, with models like the HRRR and RAP switching between the
I-94 corridor and further north towards Beaver Dam (or even
Waupun) from one initialization to the next, but the main
takeaway is we have higher confidence in the presence and
coverage of showers along and south of the I-94 corridor this
afternoon and evening.

Sheppard

&&

.SHORT TERM...
Issued 1253 AM CDT Sun Jun 21 2026

Today through Monday night:

Patchy fog early this morning will burn off quickly as the sun
rises, even with high cloud cover increasing. By mid-morning,
expecting northeasterly onshore winds to increase and steady
rainfall to spread west to east generally along and south of the
I-94 corridor. More isolated to scattered rainfall is expected
to the north of the corridor, with the NAM family still indicating
the farthest north trajectory all the way through
Marquette/Green Lake/Fond du Lac/Sheboygan during the late
afternoon to evening hours. However, with a known moisture bias,
tend to lean toward the isolated shower solutions for those areas.
In addition, global models are still showing dry conditions across
southern Wisconsin, which leads to the continued hedging against
higher PoPs along and north of the I-94 corridor. Very minimal
(~100-200 J/kg) MUCAPE exists in the 0 to -20 C portion of the
column right along the WI/IL border during the late afternoon to
evening hours, so cannot rule out an isolated bolt of lightning,
but the probability is very low (~10%).

As low pressure makes its closest approach this afternoon into
tonight, expecting gusty northeast winds to develop and persist
along Lake Michigan counties and far southern Wisconsin. Gusts 20
to 25 mph expected. With rain and onshore winds, expecting
temperatures to struggle to exit the 60s, with some areas farther
north where sunlight lingers longer seeing highs in the low 70s.

Low pressure exits to the east overnight tonight, with gusty winds
continuing and turning more northerly. Moderate to high swim risk
is expected to develop along Lake Michigan beaches during the
overnight hours, continuing into Monday, with high swim risk
generally expected Milwaukee County southward. Stay out of the
water during this period, and stay away from dangerous areas like
piers and breakwalls! Highs in the 60s are expected near Lake
Michigan, gradually increasing westward to the upper 70s in
southwest WI. Winds will gradually diminish Monday night, allowing
waves to diminish below hazardous levels. Lows Monday night in
the low 50s.

MH

&&

.LONG TERM...
Issued 1253 AM CDT Sun Jun 21 2026

Tuesday through Sunday:

High pressure persists over the Great Lakes region through
Tuesday, with low pressure deepening over the northern Plains.
Expect southwesterly winds to bring in highs in the upper 70s.
Low pressure looks to pivot northeastward into Tuesday night,
bringing the next widespread chances for rainfall to southern
Wisconsin (60-80%). Lightning will also be expected with this
rainfall, but low potential for severe at this time (time of day
and lack of LLJ dynamics lead to a very conditional threat,
especially with the parent low so far northwest).

Lingering precipitation across the Midwest along a frontal
boundary from the northern Plains low then looks to phase with a
shortwave from the southern Plains, allowing for cyclogenesis
across the Great Lakes and therefore bringing an additional wave
of precipitation on Wednesday (60-80%). The timing of this wave
looks to be more favorable, with southern Wisconsin remaining in
the warm sector. Lightning is expected, and potential for severe
may develop during the afternoon hours on Wednesday. Low pressure
exits into Wednesday night, with a cold front bringing in one last
round of showers and storms. Modeling diverges on whether low
pressure continues to bring a final shortwave of precipitation
across the region on Thursday, so left in 20-40% PoPs due to
uncertainty.

High pressure makes a brief return on Friday, but an active
pattern with frequent shortwaves propagating through the southern
Plains into the Upper Midwest will continue through the weekend.

MH

&&

.AVIATION...
Issued 530 AM CDT Sun Jun 21 2026

Dry weather and VFR continue this morning with increasing cloud
coverage at and above the 20,000 ft level. Decreasing cloud
ceilings and increasing rain chances are expected from midday
into this afternoon, with predominantly VFR cloud ceilings
(4,000 ft or higher) north of the I-94 corridor and occasional
MVFR (as low as 1,500 to 3,000 ft) cloud ceilings further south.
Similarly, the rain shower chances + coverage will be highest
further south (as seen in the TAFs). Rain will gradually taper
off west to east this evening, with winds turning northeast and
becoming breezy along the Lake Michigan shoreline. Ceilings
gradually improve west to east overnight.

Sheppard

&&

.MARINE...
Issued 1253 AM CDT Sun Jun 21 2026

Low pressure around 29.5 inches currently over the central High
Plains will progress eastward into central Illinois this afternoon
and evening, bringing increasing easterly winds to the southern
half of the open waters. Winds are expected to build waves in the
southern Wisconsin nearshore waters, potentially bringing
hazardous conditions for small craft. Winds turn northerly and
spread northward into Monday morning as low pressure exits into
the Northeast U.S. and high pressure around 30.3 inches builds
into northern Ontario. Winds remain northerly and steadily
diminish Monday night into Tuesday as high pressure builds over
the Great Lakes, with light and variable winds expected Tuesday
night. Winds shift southeasterly as low pressure develops in the
northern Plains on Wednesday, then to northwesterly as a cold
front from this low pushes eastward through the open waters.
Scattered thunderstorms are also possible ahead of and along with
this cold front. Low pressure exits to the east on Thursday,
bringing northwesterly winds and a brief return to high pressure.

MH

&&

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

$$

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