879
FXUS63 KMKX 031509 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1009 AM CDT Wed Sep 3 2025

.KEY MESSAGES...

- Showers and isolated thunderstorms will continue into the
  afternoon hours.

- Chilly low temperatures tonight, with below-normal
  temperatures continuing into this weekend.

- Additional showers and isolated storms likely (~60-75+%
  chances) Thursday night into early Friday morning.

- High temperatures slowly warm back up early next week.

&&

.UPDATE...
Issued 1009 AM CDT Wed Sep 3 2025

The back edge of the showers associated with a cold front has
moved into the northwest forecast area and will continue to
progress southeastward through late morning / early afternoon.
Could see some isolated thunder as the showers move through.
Should see a few breaks in the clouds behind the showers/front
this afternoon along with breezy northwest winds. In all, the
forecast looks on track through the rest of the afternoon.

DDV

&&

.SHORT TERM...
Issued 351 AM CDT Wed Sep 3 2025

Today and Tonight:

Synopsis/Mesoanalysis: Surface cyclogenesis is ongoing over northern
Lake Superior early this morning, with 3 AM surface observations
placing the developing area of low pressure just to the east of Isle
Royale. A cold front extends southwest from the low, with
observations placing the boundary along an approximate Bayfield to
Minneapolis axis as of 3 AM. Ahead of the front, model analysis &
the MKX VWP have shown steadily increasing winds in the 925-700 mb
layer, with weak warm advection triggering the ongoing areas of
showers from Janesville north to Markesan. Occasional lightning has
been noted within the shower activity, thanks to weak (~250-500
J/kg) MUCAPE in place across the region. Said areas of showers &
isolated storms will continue to move east-southeast through
daybreak, with additional shower and isolated storm development
anticipated this morning & afternoon as the cold front moves in from
the north. Apart from quick heavy downpours and a few lightning
strikes, hazardous weather is not anticipated in this activity.
Conditions will dry out this evening as winds turn northwesterly &
usher a drier air mass into the region. Said northwest winds will
also pull a much cooler Canadian air mass into southern Wisconsin,
with chilly low temperatures anticipated Friday morning.

Rest Of Overnight through Today: Showers and isolated storms will
increase in coverage this morning, lasting into the afternoon hours.
Precipitable water values of 1-1.5 inches will support brief heavy
downpours---especially in embedded storms---though fast shower/storm
motions will keep hydro concerns minimal. Expect 0.1-0.25" rainfall
totals to be the norm across the majority of the region, with
embedded pockets of higher (~0.5-0.75"+) totals where embedded
thunderstorms track. Don`t anticipate any severe weather hazards in
today`s activity, but will be monitoring for an isolated stronger
wind gust (~30-40 MPH) in embedded storms given dynamic wind fields
at the 850 mb level. Grab an umbrella or jacket before heading out
the door this morning.

Tonight: The arriving much cooler Canadian air mass will result in
chilly overnight lows, particularly away from the immediate Lake
Michigan shoreline. Anticipate widespread temps in the lower 40s,
with pockets of upper 30s readings possible in low-lying spots.
While well below early September normals, these readings will likely
fall a touch short of record levels (41 in Milwaukee; 35 in
Madison). Northwest winds will taper as the night progresses, but
will remain just elevated enough to support feel-like temps in the
mid-upper 30s north & west of Milwaukee. Be sure to grab a light
jacket if heading outdoors late tonight/early Thursday morning.

Quigley

&&

.LONG TERM...
Issued 351 AM CDT Wed Sep 3 2025

Thursday through Tuesday:

Westerly winds continue on Thursday as the occluded low continues to
spin in northern Ontario, with temperatures in the mid-60s expected
across southern Wisconsin. A clipper system develops in the northern
Canadian Prairies and swings southeastward quickly along the
southern edges of the upper level low, bringing in a quick cold
front and associated precipitation (60-80% chances) Thursday night
into Friday morning. With low temperatures around 50 degrees
Thursday night and minimal instability, not expecting lightning with
this activity. Waterspouts may be possible behind the cold front, as
the clipper does look to progress through the middle of Lake
Michigan.

As the clipper exits to the northwest along the upper level low, it
becomes absorbed into the center of the occluded low in Ontario into
Saturday. A few wrap-around showers are possible Friday, but chances
remain low at this time (~10% chance). Expect west- northwesterly
flow to bring highs in the low 60s and lows in the low 40s Friday
and Saturday. The combined low then propagates eastward as high
pressure returns to the western Great Lakes Saturday night into
Sunday, allowing temperatures to climb back to near 70 degrees
Sunday and Monday.

Tuesday, expect southerly flow to return to the region as low
pressure develops in the northern Plains, bringing temperatures in
the low 70s and potential for showers (15-25% chance) along a warm
frontal feature developing over Wisconsin.

MH

&&

.AVIATION...
Issued 1009 AM CDT Wed Sep 3 2025

The back edge of the showers associated with a cold front has
moved into the northwest forecast area and will continue to
progress southeastward through late morning / early afternoon.
Could see some isolated thunder as the showers move through. IFR
to MVFR ceilings will persist into at least early afternoon.
Should see a few breaks in the clouds behind the showers/front
this afternoon along with breezy northwest winds. Clouds bases
may raise to VFR by mid/late afternoon, with decreasing skies
expected this evening and overnight.

DDV

&&

.MARINE...
Issued 351 AM CDT Wed Sep 3 2025

1002 mb low pressure is centered over Lake Superior this morning,
resulting in breezy southwest winds across the open waters of Lake
Michigan. Said low will progress toward the Ontario-Quebec border
today, deepening to near 996 mb in the process. Breezy southwest
winds will thus continue into this morning, with gusts in the 20-25
knot range anticipated across all of Lake Michigan. A few gusts
could briefly gale-force, particularly across the northern third of
the waters. Winds will quickly shift out of the northwest this
afternoon and evening as a cold front moves across the waters.
Additional gusts in the 20-25 knot range are anticipated during and
immediately following the frontal passage. Winds will taper tonight
as 1012 mb high pressure settles into the northern Great Plains.

High pressure will progress east into the western Ohio River Valley
on Thursday, allowing winds to turn out of the southwest by the
early afternoon hours. Winds will quickly become gusty Thursday
evening into predawn Friday morning as a second area of 1000 mb low
pressure approaches Lake Michigan from the northern Great Plains.
The low will cross the waters near/just after daybreak Friday
morning, resulting in a west-northwest wind shift from late morning
into the early afternoon. Gale force gusts are expected over at
least the southern half of Lake Michigan as the low approaches and
crosses early Friday morning. Headlines will become necessary in
subsequent forecasts. Gusts will begin to taper Friday afternoon and
evening as the aforementioned low moves into Quebec.

Showers and isolated thunderstorms are likely this morning and
afternoon as a cold front moves south across Lake Michigan. Severe
weather is not expected, though a few storms could produce brief
gusty winds. A few waterspouts are possible in embedded
thunderstorms, particularly across the northern half of Lake
Michigan. Scattered lake effect showers will remain possible through
the day on Thursday over far northern Lake Michigan. Additional
isolated waterspouts are possible in this activity. Showers and
isolated thunderstorms are likely early Friday morning ahead of the
approaching second area of low pressure.

Northwest winds will become gusty in nearshore zones late this
afternoon through the first part of this evening behind the
departing cold front. A few gusts could briefly approach Small Craft
Advisory thresholds, particularly between 7 PM - 1 AM CDT. Given the
expected brief and isolated nature of any such gusts, Small Craft
Advisories aren`t anticipated at this time. Periods of showers and
embedded thunderstorms will also accompany the approaching/passing
cold front, with the best chances being this morning and afternoon.
Southwest winds quickly become gusty Thursday night ahead of a
second area of approaching low pressure, ultimately shifting out of
the west-northwest by sunrise Friday as the low departs to the east.
Widespread gusts at and above Small Craft Advisory levels are
expected during this time frame, with a few gusts approaching gale
force during the predawn hours Friday. Small Craft Advisories will
become necessary in subsequent forecasts.

Quigley

&&

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

$$

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