Small Craft Advisory 83, NWS Milwaukee, WI

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
630 PM CDT Tue Sep 15 2026

.KEY MESSAGES...

- Lingering rain / drizzle chances (10-30%) tonight through
  Wednesday, mainly near and south of the WI/IL border. A stray
  rumble of thunder can't be ruled out, but would mainly be
  confined south of the state.

- Region-wide rain chances (35%) late Wednesday night into
  Thursday morning. A stray rumble of thunder can't be ruled
  out.

- Higher chances for showers and storm arrive Friday / Friday
  night and continue off and on through early next week.

&&

.UPDATE...
Issued 635 PM CDT Tue Sep 15 2026

Forecast is on track this evening. A residual stationary front
is draped over central Illinois, with a scattering of strong-
severe convection ongoing from Quincy toward Kankakee. Elevated
frontogenesis to the north of the boundary is supporting lighter
precipitation near & just south of the Wisconsin-Illinois
border, with recent radar trends showing activity pushing out of
southeast Wisconsin. Expect the elevated FGEN precip to
continue to shunt south through the overnight as high pressure
builds into north-central Wisconsin from the Great Plains.

Quigley

&&

.SHORT TERM...
Issued 255 PM CDT Tue Sep 15 2026

Tonight through Wednesday night:

The surface frontal boundary is progged to remain stalled south
of the region through the period, leaving us with seasonably
cool and humid weather with mostly cloudy skies and some
occasional drizzle / sprinkles of rain. The best chances (30%)
for some measurable rainshowers (with a stray rumble of thunder
possible) would be along and south of the WI/IL border tonight
into Wednesday. Some region-wide ~35% chances for rain are in
the forecast late Wednesday night into Thursday morning as a
weak low pressure system (barely resolved even on high-res
guidance) crosses WI and allows some weak LLJ / WAA activity at
850-700mb to move into the region; only concern there would be
a stray rumble of thunder. Other than that, all we've got is
enough mid-level isentropic upglide (north of the surface
front) to keep the skies cloudy and maintain occasional drizzle
/ sprinkle chances.

A Moderate Swim Risk remains in effect until this evening for
Lake MI beaches in Sheboygan and Ozaukee counties. Waves should
continue to slowly decrease as winds veer west (offshore). Some
steady northeast winds late tonight through Wednesday morning
could boost wave heights to the ~4.0 ft mark for Ozaukee,
Milwaukee, Racine, and Kenosha counties, allowing Moderate Swim
Risk conditions to return. A High Swim Risk cannot be
completely ruled out if northeast winds exceed expectations.

Sheppard

&&

.LONG TERM...
Issued 250 PM CDT Tue Sep 15 2026

Thursday through Tuesday:

While the surface frontal boundary will be south of the WI/IL
border Thursday morning, the broad, weak 850mb front will
continue to sit over northern IL. While the overall forcing will
be too weak for an organized area of rain, we cannot rule out a
few light showers or sprinkles through the whole day. In
addition, there could be a push of cooler air down the axis of
Lake Michigan that converges over southeast WI and could produce a
few showers along it in the late afternoon and evening.

Warm air advection will resume Thursday night over eastern Iowa.
This is associated with a mid level shortwave trough
approaching from the northern Plains. The 850mb warm front (and
rain) will slowly spread into southwest WI Friday morning.
However, the system will be occluding which will slow down the
progression of this front into southern WI.

There is highest confidence in widespread showers and a few
thunderstorms impacting southern WI from late Friday evening
through Saturday morning. This is when the mid level shortwave
trough and surface low track across southern WI. We will have the
front focused right overhead for about a twelve hour period with
the low level jet veering right over us, precipitable water values
will be around 2 inches again, and we will be along the
instability gradient. These ingredients put us in a favorable
position for a heavy rain risk. Keep up with the forecast with
this scenario.

Sunday is looking drier for us, although lingering clouds and
light rain/sprinkles should still be possible. Then yet another
mid level shortwave trough trekking across the Northern Plains
will arrive in the Upper Midwest by Sunday night or Monday morning
and bring more rain chances to southern WI.

Cronce

&&

.AVIATION...
Issued 635 PM CDT Tue Sep 15 2026

Mostly VFR flight categories prevail through the remainder of
this evening through the day Wednesday. Can't rule out some
brief periods of -RA & MVFR CIGs in far southeast Wisconsin
through mid-evening, with potential shunting south of the
Wisconsin-Illinois border from the second half of the evening
onward. High pressure will nudge into northern Wisconsin
tonight, bringing a north-northeast wind shift at all terminals.
The high will continue east through Wednesday, bringing an
east-southeast wind shift by mid-late afternoon. Warm advection
will increase regionally Wednesday evening, with gradually-
lowering CIGs eventually leading to MVFR conditions overnight.
Rain showers may accompany the lowering CIGs. Have accounted for
this potential at the conclusion of the 30 hour period at MKE,
with mentions becoming necessary in the 06Z update at other
terminals.

Quigley

&&

.MARINE...
Issued 250 PM CDT Tue Sep 15 2026

Scattered showers and weak thunderstorms remain possible over
southern portions of the lake later today through Wednesday as a
frontal boundary remains stalled south of the lake. A separate
cold front is set to cross the lake later this afternoon,
allowing the ongoing breezy southwest winds to veer northwest
and decelerate.

High pressure around 30.4 inches will track east across southern
Ontario Canada late tonight through Wednesday, veering winds due
north then northeast. Predominantly light and variable winds
expected late Wednesday night through Thursday as additional
high pressure forms over Manitoba and weakens the pressure
gradient.

Breezy east to northeast winds may then develop late this week
into this weekend as the aforementioned high pressure shifts
east across Ontario Canada and low pressure spreads east from
the Great Plains. The gradient between these two systems could
drive gusty winds from various directions depending on system
track, though our best guess is predominantly east (northeast to
southeast) for the time being.

Nearshore Zones:
For zones south of Port Washington, expecting waves to approach
the 4 ft mark for a brief period Wednesday morning, and a Small
Craft Advisory is possible depending on confidence / duration.
Small Craft Advisory conditions are looking likely at times this
weekend for all nearshore zones due to gusty east winds and
building waves.

Sheppard

&&

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

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