NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 241026 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
526 AM CDT Thu Sep 24 2026

.KEY MESSAGES...

- High Swim Risk conditions continue through the first half of
  today for all beaches along Lake Michigan.

- Slightly below normal temps continue for the next several
  days.

&&

.UPDATE...
Issued 526 AM CDT Thu Sep 24 2026

Low cloud decks have generally cleared most of the area, though
parts of far southeast and far southwest Wisconsin may see these
clouds linger for another few hours. There is also some ground
fog in low areas that may linger until after sunrise.

Middle to high clouds will gradually move east into the area
today. Cool temperatures will linger under light east winds.

A shortwave trough will move southeast toward and through the
area tonight into Friday morning. Forecast soundings are showing
the air column saturating in western parts of the area later
tonight into Friday morning, with drier air to the east. CAMs
are showing and area of light showers trying to move east
across the area during this period. For now, kept 20 to 30
percent chances for showers across the western parts of the area
for now. Not sure if this will affect areas to the east,
depending on how much moisture is available.

Wood

&&

.SHORT TERM...
Issued 1000 PM CDT Wed Sep 23 2026

Thursday through Friday night:

Cool and predominantly dry weather should continue through the
end of the work week. High pressure remains dominant over
southeastern Canada through the period, driving an easterly
breeze at times. With a slightly tighter pressure gradient over
Lake MI, this steady breeze should hold waves around 3 to 4
feet, locally higher to 5 feet. Hence, a High Swim Risk remains
in effect for all Lake MI beaches in the CWA through early
Thursday afternoon. Winds will remain easterly thereafter, but a
diminishing pressure gradient (as the core of the high pressure
system drops several millibars) should then allow winds and
waves to fall below critical thresholds.

Southern WI will remain on the periphery of a slightly more
humid airmass just to the south, yielding intermittent periods
of stratocumulus cloud cover (similar to what we observed this
past afternoon). Late Thursday evening through early Friday
morning, CAMs indicate a partial breakdown of the low-level dry
air, with some cyclonic flow aloft allowing these clouds to
produce some light rainshowers, mainly south and west of Madison
(though the 21z RAP depicts it more widespread). In any case,
this activity would wrap up by mid morning Friday and leave
predominantly dry weather through the rest of the day.

Sheppard

&&

.LONG TERM...
Issued 1000 PM CDT Wed Sep 23 2026

Saturday through Wednesday:

For this weekend into early next week, a longwave upper ridge
holds its ground over the western Great Lakes, allowing
predominantly dry and quiet weather to prevail. Surface high
pressure weakens but remains present across the Great lakes as
well, with a light east to southeast breeze expected, nearly
calm at times. Temperatures remain slightly below seasonal
norms. Portions of southwestern WI may observe some slight
chances for rain in the forecast at times (mainly below 25%
chance, confined south and west of MSN) as shortwave troughs
attempt to crest the ridge.

Monday night into Tuesday, an organized upper trough becomes
established over the Dakotas / Nebraska, which will then track
eastward across the Midwest and likely result in strong
cyclogenesis midweek. Rain chances spread into the region from
west to east on Tuesday, with rain looking likely at some point
Tuesday night or Wednesday as surface low pressure deepens and
tracks northeastward past the region (exact track is uncertain).

Sheppard

&&

.AVIATION...
Issued 526 AM CDT Thu Sep 24 2026

Low cloud decks around 3500 feet AGL or so have generally
cleared most of the area, though parts of far southeast and far
southwest Wisconsin may see these clouds linger for another few
hours. There is also some ground fog in low areas that may
linger until after sunrise.

Middle to high clouds will gradually move east into the area
today, continuing tonight into Friday. There may be some
scattered stratocumulus clouds around 3500 feet AGL as well.
Light east winds are expected today into Friday.

Showers are possible across the western parts of the area later
tonight into Friday morning, including Madison and Janesville.
Not sure if this will affect areas to the east.

Wood

&&

.MARINE...
Issued 1000 PM CDT Wed Sep 23 2026

Open Waters / Synopsis:
Strong high pressure around 30.6 inches will linger over
southern Ontario and Quebec Canada through the overnight hours,
weakening to 30.4 inches through Thursday. Modest easterly
winds continue through Thursday morning, weakening into the
afternoon. Light east to southeast winds then prevail for the
rest of the week and into the weekend as the high reorients
from the northern Great Lakes to James Bay.

Nearshore Zones:
The steady onshore winds overnight through Thursday morning
should boost waves to around the 4 ft mark, locally higher. As
such, a Small Craft Advisory remains in effect until early
Thursday afternoon. Winds do remain easterly thereafter, but
gradually diminish in intensity, along with the waves.

Sheppard

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052-WIZ060-WIZ066-WIZ071-WIZ072
     until 1 PM Thursday.

LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 1 PM
     Thursday.

&&

$$

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