937
FXUS63 KMKX 140253
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
953 PM CDT Mon Oct 13 2025

.KEY MESSAGES...

- A few areas of fog ongoing along and east of a Janesville to
  Fond du Lac line, with some locally dense patches already
  reported. Fog will dissipate towards dawn Tuesday.

- Additional rain chances (~40-70%) return to southern Wisconsin Tuesday
  night.

- Active end to the week with several opportunities for showers
  and a few thunderstorms Thursday through Sunday.

&&

.UPDATE...
Issued 940 PM CDT Mon Oct 13 2025

Along and east of a Janesville to Fond du Lac line, we are
beginning to see some fog development as low level cloud cover
pushes southeast of the area, with some localized areas already
meeting dense criterion. Some scattered high altitude clouds
have arrived, but are failing to inhibit the growth of the fog
according to recent METAR reports.

Further west of the aforementioned area, any fog that does
develop would likely only be patchy and hold short of dense
criterion. Lone Rock WI, for example, currently has an 8 degree
fahrenheit dewpoint depression, with the scattered high
altitude clouds offering some resistance to radiational cooling.
Eastern areas appear more susceptible to fog due to a lack of
heating and persistent areas of drizzle this past afternoon,
which has since ended. In contrast, western areas have received
some light northwesterly dry air advection and were mostly

Late overnight towards dawn Tuesday, a dry cold front pushes
through, allowing north winds to ventilate shoreline areas and
possibly help with dissipating the fog. That being said, some
model guidance (including our blended NBM guidance) suggests
that the fog may hang on until the sunrise begins to burn it off
Tuesday morning.

Sheppard

&&

.SHORT TERM...
Issued 258 PM CDT Mon Oct 13 2025

Rest Of This Afternoon through Tuesday night:

Synopsis/Mesoanalysis: Surface observations place a cold front along
an approximate Fond du Lac - Beaver Dam - Janesville axis early this
afternoon. Forming in advance of the aforementioned front, earlier
day rain showers have largely concluded, though light drizzle & low
clouds continue to be reported in the vicinity of the Kettle
Moraine. Clouds are beginning to break further west, where post-
frontal subsidence is allowing the lower part of the column to dry
out. Developing in response to upper ridging building over the
Northern Plains, high pressure is apparent along the North Dakota-
South Dakota border. Both the upper ridge & its attendant surface
high will progress toward Lake Superior by daybreak Wednesday.
Rounding the crest of the ridge, an upper jet streak will move
across the western Great Lakes Tuesday evening & night, with its
right entrance region advancing from the Missouri Valley to southern
Wisconsin in the process. Lift from the passing right entrance
region will combine with increasing warm advection in the lower
atmosphere to support returning rain chances Tuesday evening into
the predawn hours Wednesday. Onset of rainfall will be gradual
during this time frame, as precipitation will need to overcome very
dry low level air. Hazards are not anticipated in any rainfall
occurring Tuesday evening and night.

Rest Of This Afternoon: Lingering drizzle and light rain showers
will conclude by mid-afternoon as a cold front progresses through
the area & drier air advects in from the northwest. Additional
accumulations will be light to negligible.

Tuesday Night: Rain chances will gradually trend upward as large
scale ascent increases across southern Wisconsin. Precip will need
to overcome a dry near-surface layer materializing in the wake of
today`s frontal passage, which should keep measurable precip away
until the later evening hours. Forecast soundings show negligible
instability, which should keep thunder & lightning potential
minimal. Lack of embedded convection will keep rain fall rates down,
with most locations expected to see new rainfall totals at or below
one tenth of an inch.

Quigley

&&

.LONG TERM...
Issued 258 PM CDT Mon Oct 13 2025

Wednesday through Monday:

Synopsis: Rain showers will wrap up during the morning hours
Wednesday as upper divergence shifts east & attendant low level warm
advection wanes. Upper ridging and accompanying surface high
pressure will progress across the area on Wednesday, resulting in
mostly sunny skies & pleasant conditions. A pair of upper troughs
will influence the end of week weather, which features increasing
surface temperatures & returning rain chances. The first will eject
into the Northern Plains Thursday night, crossing the US-Canadian
border by Friday evening. The second will then drive into the Upper
Mississippi Valley Friday night through Saturday, pulling a surface
cold front across southern Wisconsin in the process. The cold front
is forecast to be out of the region by Sunday morning, with gusty
north-northwest winds bringing cooler Canadian air to the area.
Ridging will shift across the western Great Lakes Sunday night into
Monday, allowing southwest winds to bring milder air back to
southern Wisconsin. How progressive upper ridging will be---and thus
how quickly warmer temperatures will work back into the region---
remains a source of disagreement in global forecast guidance.
Trends will be monitored in coming forecasts.

Thursday through Thursday Night: Rain chances return to the forecast
as upper divergence & low level warm advection increase ahead of the
Northern Plains upper trough. Current forecast guidance suggests
that the best overlap of warm advection & upper divergence will be
centered across northern Wisconsin and the Upper Peninsula of
Michigan, with southern Wisconsin being on the southern edge of the
more favorable forcing. Have thus maintained NBM precip
probabilities in the afternoon update, which paints ~15-30% values
largely along/north of I-94. Medium-range forecast guidance shows
most instability remaining west of the area through this time frame,
which should keep thunder potential low in any Thursday-Thursday
night rainfall.

Friday Night through Saturday Night: Anticipate higher rainfall
potential areawide as deeper synoptic forcing moves overhead. Peak
precip chances will be centered on the passage of the upper wave &
affiliated surface front, with a range of possible passage timings
being shown in current forecast guidance. Timing trends will thus be
monitored in coming forecasts. Should a daytime passage become
favored, a few embedded thunderstorms would be possible.

Quigley

&&

.AVIATION...
Issued 940 PM CDT Mon Oct 13 2025

Areas of fog in east-central and southeastern Wisconsin
counties expected to occasionally reduce visibility to 1/4 SM
through the rest of the overnight hours, burning off after
sunrise Tuesday. A Dense Fog Advisory has been issued for the
affected area. Along the immediate Lake MI shoreline, even
terminals that aren`t already experiencing dense fog (for
example, KMKE), the low ceilings evolving from the nearby
patches of fog are still LIFR at times. Further west of the
advisory, fog is expected to remain patchy / not particularly
dense due to some dry air intrusion.

Fog and low ceilings gradually dissipate after sunrise Tuesday,
with dry weather and VFR expected through the rest of the
daytime hours. Some scattered high altitude clouds are to be
expected, perhaps with some additional scattered lake effect
clouds off of Lake Michigan. North to northeast winds across the
area, breezy along the shoreline.

Rain showers expected to push in from the west Tuesday evening
through Tuesday night. No thunder expected from this activity at
this time.

Sheppard

&&

.MARINE...
Issued 258 PM CDT Mon Oct 13 2025

995 mb low pressure is moving into the Hudson Bay this afternoon,
resulting in generally east to southeast winds across the open
waters of Lake Michigan. Said low will drag a cold front across the
lake this evening, resulting in a breezy northerly wind shift.
Breezy north to northeast winds will continue Tuesday through
Tuesday night as 1030 mb high pressure builds into the northern
Great Plains. The high will cross Lake Michigan on Wednesday,
allowing winds to taper across the waters. Winds will turn out of
the south to southeast on Thursday, when 1000 mb low pressure is
forecast to develop over the northern Great Plains. The low will
deepen to near 992 mb near Lake Winnipeg Thursday night through
Friday, allowing winds to increase further across Lake Michigan.
Gusts could approach gale force during this time frame, with trends
being monitored through the coming forecasts. Winds will remain
breezy as they turn out of the southwest on Saturday. Winds will
increase again as they turn out of the northwest on Sunday behind a
cold front. Additional gales will be possible as this occurs.

Breezy northeast winds will result in elevated wave heights in
nearshore zones Tuesday morning through Wednesday morning,
particularly from Port Washington south to Winthrop Harbor. A Small
Craft Advisory has been issued between 7 AM CDT Tuesday and 7 AM CDT
Wednesday given this potential. Advisory extensions may be needed in
later forecasts from Racine south to the state line, where waves
will remain elevated a touch longer. Wave heights will taper by late
Wednesday morning. Winds and waves will increase once again Thursday
night into Saturday morning, when additional Small Craft Advisories
will be needed. A few gusts could approach gale force, particularly
Friday afternoon through Friday evening. Conditions will improve
slightly during the day Saturday ahead of an approaching cold front.
Winds will increase once again behind the front Sunday, resulting in
additional Small Craft Advisory conditions.

Periods of showers will accompany the series of low pressure &
frontal passages through this weekend. Peak periods of shower
potential will be through this evening, Tuesday night, and Thursday
through Saturday. A few rumbles of thunder could accompany showers,
though severe weather is not anticipated at this time.

Quigley

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ644-LMZ645-LMZ646...7 AM Tuesday to
     7 AM Wednesday.

&&

$$

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