705
FXUS63 KMKX 011423 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
923 AM CDT Mon Sep 1 2025

.KEY MESSAGES...

- Fog is possible again later tonight into early Tuesday
  morning, with patchy dense fog possible in low lying areas.

- Shower are likely (60 to 80 percent chances) with some
  thunderstorms later Tuesday night through Wednesday along a
  cold front.

- Below normal temperatures expected Wednesday night through the
  end of the week.

- Additional periods of showers and isolated storms are possible
  (20 to 40 percent chances) on Friday.

&&

.UPDATE...
Issued 923 AM CDT Mon Sep 1 2025

Most of the lingering fog in the Wisconsin River Valley and
other low areas will end shortly, with continued daytime
heating. There may be scattered diurnal cumulus clouds that
develop by midday into this afternoon. Light east to southeast
winds are expected.

High pressure to the east will keep dry conditions across the
area into Tuesday. Light to calm winds later tonight into early
Tuesday morning should allow for another round of shallow fog
along and west of the Kettle Moraine. Patchy dense fog may occur
in low lying areas, as the inversion may be a little stronger
than the past few nights and low temperatures dropping a few
degrees below the lowest dew points from this afternoon.

Highs should reach the middle 70s today, with middle to upper
70s on Tuesday. Lows tonight should be in the lower to middle
50s.

Wood

&&

.SHORT TERM...
Issued 333 AM CDT Mon Sep 1 2025

Today through Tuesday:

Synopsis/Mesoanalysis: A broad area of high pressure extends from
the Saint Lawrence River west to the Upper Mississippi Valley this
morning, maintaining clear skies and light surface winds across
southern Wisconsin. Efficient radiational cooling has occurred in
the presence of the clear skies and winds, with areas of mostly
shallow ground fog having been noted in recent observations.
Slightly deeper valley fog has developed from Sauk City west to
Prairie du Chien, and is well-defined in current nighttime
microphysics imagery. Areas of patchy ground fog, in addition to
valley fog near the Wisconsin River, will continue through daybreak,
with visibilities rapidly improving after sunrise. Well to the north
of the region, surface observations show a nearly stationary surface
front extending from the Hudson Bay into Saskatchewan. Even further
northwest, water vapor imagery shows an upper trough along the
border of Alberta and the Northwest Territories. The trough is
forecast to dig southeast today through Tuesday, dragging the
currently stationary Hudson Bay - Saskatchewan surface front with it
by Tuesday afternoon. The pair of features will continue to drive
toward the international border Tuesday evening, reaching the Upper
Mississippi Valley by predawn Wednesday morning. Shower and storm
chances thus return to the forecast late Tuesday night, particularly
along & north of US-151.

Rest Of Overnight: Expect current trends showing areas of fog
along/west of the Kettle Moraine to continue through daybreak.
Similar to last night, forecast soundings show an extremely shallow
layer of near-surface saturation outside of the immediate Wisconsin
River Valley, which likely helps to explain the high variation in
hour to hour visibilities being reported at impacted observation
sites (JVL, UES, ETB, and MSN to name a few). Given these trends,
don`t anticipate the need for Dense Fog Advisories through sunrise,
but will nevertheless be closely watching surface ob & webcam
trends. If < 1 mile visibilities become more prevalent outside of
low-lying spots, Special Weather Statements may be considered. Slow
down, use low beam headlights, and allow for extra following
distance if encountering areas of ground fog through daybreak.

Tonight: With largely unchanged surface conditions, expect another
round of ground fog development along and west of the Kettle
Moraine. Budget a few extra minutes of travel time if taking to the
roads late tonight/early Tuesday morning.

Tuesday Night: Shower and thunderstorm chances will begin to
increase after midnight as the aforementioned upper trough and
surface front begin to approach the region. Expect that the majority
of precip potential will remain along and north of US-151, where
proximity to the approaching features will be greatest through
sunrise. Don`t currently anticipate any strong/severe storms in this
activity given overnight timing, though storms could produce brief
heavy downpours.

Quigley

&&

.LONG TERM...
Issued 333 AM CDT Mon Sep 1 2025

Tuesday night through Sunday:

A robust mid level shortwave trough over central Canada will swing
across the MN/Ontario border Wednesday morning and bring us our
first glimpse of Fall. Ahead of this wave, surface low pressure will
develop over Ontario, and the associated cold front will approach
northwest Wisconsin Tuesday and Tuesday night. We can expect
increasing southerly winds ahead of this front. The cold front will
cross southern WI on Wednesday, although the timing is uncertain.
Showers and thunderstorms are likely along the front. If it is later
in the day, there will be time for temps to reach 70s one more time,
and also a potential for a few stronger storms.
If it crosses in the morning, there will be less instability and
weaker convection.

Brisk northwest winds will usher colder air into the area behind the
front Wednesday night into Thursday. Highs Thursday will be around
60. Another shortwave trough is expected to swing across MN and WI
Thursday night and bring a reinforcing blast of cool air on gusty
WNW winds on Friday. We should see some showers along this secondary
cold front. The upper trough will begin to move out on Saturday,
although a few light showers are possible before it completely
exits.

Cronce

&&

.AVIATION...
Issued 923 AM CDT Mon Sep 1 2025

Most of the lingering fog in the Wisconsin River Valley and
other low areas will end shortly, with continued daytime
heating. There may be scattered diurnal cumulus clouds around
3500 feet AGL that develop by midday into this afternoon. Light
east to southeast winds are expected.

High pressure to the east will keep dry conditions across the
area into Tuesday. Light to calm winds later tonight into early
Tuesday morning should allow for another round of shallow fog
along and west of the Kettle Moraine. Patchy dense fog may occur
in low lying areas.

Winds will become southwest on Tuesday, with south to southeast
winds for terminals near Lake Michigan Tuesday afternoon. More
scattered diurnal cumulus clouds around 3500 feet AGL may occur
by midday into the afternoon.

Wood

&&

.MARINE...
Issued 923 AM CDT Mon Sep 1 2025

High pressure around 30.3 inches will linger over the region
into Tuesday morning, with light winds. South to southwest winds
will become established late Tuesday afternoon through Tuesday
night, as low pressure around 29.6 inches develops across Lake
Superior.

The low will slowly move east toward the Ontario and Quebec
border Wednesday, dragging a strong cold front across Lake
Michigan. Gusty northwest winds will become established along
and behind the passing front Wednesday evening through Thursday
morning. Widespread gale force gusts are not anticipated at this
time, though forecast trends will be closely monitored.

Winds are forecast to turn west southwest Thursday afternoon
and night, as another low pressure system around 29.4 inches
develops somewhere across the western Great Lakes region.
Additional gusty winds will be possible during this time. The
low will cross over or just to the north of Lake Michigan during
the day on Friday, resulting in a northwest wind shift Friday
night into Saturday. Periods of Small Craft Advisory conditions
are possible Wednesday into Friday across the nearshore waters.

Showers are expected, with some thunderstorms, along the
advancing cold front Wednesday and Wednesday evening. A few
storms could produce gusty winds. Forecast trends will also be
monitored for waterspout potential during the day on Wednesday,
particularly across the northern half of the open waters.

Additional showers and isolated thunderstorms will be possible
ahead of the second low on Friday. Whether or not gusty winds or
waterspouts will accompany this activity remains uncertain at
this time.

Quigley/Wood

&&

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

$$

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