NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 091744
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1244 PM CDT Wed Sep 9 2026

.KEY MESSAGES...

- Patchy fog possible later tonight, particularly in low-lying spots.

- Warm but less humid conditions through the end of the work
  week. No rain expected.

- Shower & thunderstorm chances return late Friday night into
  Saturday and Sunday night into Monday.

&&

.SHORT TERM...
Issued 1250 PM CDT Wed Sep 9 2026

Rest of this Afternoon through Friday:

Synopsis/Mesoanalysis: A cold front is working through southern
Wisconsin early this afternoon, with several areas of surface
convergence making the location of the boundary somewhat diffuse.
Latest best-guess analyses place the front along a Sheboygan-Ripon-
La Crosse axis, with 3-5+ degree north-south dew point differences
evident along certain segments of the boundary. Skies have cleared
nicely ahead of the front, making cross-frontal temperature
differences negligible. The cold front will slowly continue to work
its way south through the remainder of the afternoon & into this
evening, with noticeably drier air becoming established areawide by
midnight. The drier air will remain entrenched through the day on
Thursday as high pressure moves across the area. The high will shift
east on Friday, with southerly return flow bringing slightly muggier
but still comfortable conditions to the region.

Rest of this afternoon: Cold front will continue to move south
through the area, gradually pulling lower dew points into
northwestern counties. Despite clearing skies that have materialized
in advance of the front, weak along-frontal convergence & an absence
of other forcing mechanisms make pop-up precip potential low along
the front.

Tonight: With high pressure nudging in from the west, resulting
clear skies & relaxing surface winds could be supportive of some
patchy fog development closer to daybreak. Near-surface moist layers
will be shallow & susceptible to mix out, so expecting best fog
potential to be in low-lying areas. Not expecting any patchy fog to
be dense, but will be monitoring trends into tonight. Slow down, use
low beam headlights, and allow for extra following distance if
encountering patchy fog on roads later tonight.

Quigley

&&

.LONG TERM...
Issued 1250 PM CDT Wed Sep 9 2026

Friday night through Wednesday:

Synopsis: A pair of upper disturbances remain on track to move
through the region Friday night through Saturday & Sunday night
through Monday. Each is expected to bring periods of showers and
thunderstorms to southern Wisconsin, with precipitation focusing
along wings of warm/moist advection leading each system & along
trailing cold fronts. Current timing points toward warm advection
precip occurring during overnight & predawn periods, with any cold
frontal development favored during the following afternoons.
Afternoon/cold frontal storm coverage will be dependent on
sufficient thermodynamic recovery in each system. Humid conditions
will occur in the interim warm sectors on Saturday/Monday
afternoons, with air temperatures expected to remain low enough to
preclude to need for heat headlines. High pressure will slide into
the western Great Lakes Tuesday-Wednesday, bringing dry and pleasant
conditions for the middle of next week.

Friday night through Saturday: First of two primary long term period
precip windows opens across southern Wisconsin. Anticipating a warm
frontal boundary to work into the area late Friday night/predawn
Saturday morning, with affiliated shower and thunderstorm chances
spreading in after midnight. Overnight storm timing should dampen
widespread severe weather potential, but will need to monitor for an
isolated storm with gusty winds given building MUCAPE and increasing
deep layer shear. Does appear that there will be an intermediate dry
period ahead of the encroaching cold front Saturday
morning/afternoon, with a second chance for showers/storms arriving
with the boundary during the later afternoon & evening. Earlier day
sunshine will be a requisite for afternoon/evening storms, with any
combination of overcast skies or lingering rain greatly reducing
potential. Currently appears that the best chances for recovery will
be in south-central and southeast Wisconsin, where the front will
arrive latest in the day. Have thus maintained precip probs
from the NBM in the afternoon update, which at-present appear
representative of atmospheric expectations. In the event re-
development occurs, an isolated stronger storm with gusty winds
would be possible.

Sunday evening through Monday: A second (and potentially more
dynamic) system will move through the region, bringing storm chances
Sunday evening/night & once again Monday afternoon/evening. Initial
global guidance points toward greater mass fluxes into this second
system, which would in turn lead to greater instability, deep layer
shear, and precipitable water values for showers & storms to work
with. Will thus need to monitor for some stronger storms with
locally heavy rainfall during this portion of the period, with the
understanding that changes in system strength will lead to changes
in possible hazards. Will start providing more granular details from
late week into the weekend as high-res guidance comes into range.

Quigley

&&

.AVIATION...
Issued 1250 PM CDT Wed Sep 9 2026

A mix of flight categories prevails early this afternoon as a cold
front moves through, with generally VFR conditions north & MVFR/IFR
categories further south. Have adjusted immediate near-term
forecasts from observational trends at each site, with the
expectation for prevailing VFR categories to return at all
aerodromes by mid-afternoon. West-northwest winds will occasionally
be gusty behind the departing cold front through early evening, with
winds trending variable as high pressure approaches later tonight.
Generally light winds will continue through the day Thursday as said
high moves across southern Wisconsin. Patchy fog is possible later
tonight, particularly in low-lying spots. Attendant VIS reductions
would lead to sporadic MVFR or IFR flight categories if they
materialized in the vicinity of an aerodrome, though confidence in
development is too low to justify any mentions in current forecasts.
Will be monitoring trends for any amendments into this evening.

Quigley

&&

.MARINE...
Issued 1250 PM CDT Wed Sep 9 2026

Low pressure near 980 mb will continue across the southern Hudson
Bay through today, gradually pulling a cold front across the open
waters of Lake Michigan. The passing boundary will bring a west-
northwest wind shift across Lake Michigan by late afternoon. Shower
& embedded thunderstorm chances will continue along/ahead of the
passing front, with severe weather not expected. High pressure near
30.1 inches will build in from the northern Great Plains tonight,
lingering through Thursday night & bringing light and variable winds
to the waters.

A new area of low pressure near 1018 mb will shift from central
Canada toward the Hudson Bay Friday morning through the day
Saturday, bringing increasing south-southwest winds followed by a
west-northwest wind shift behind a cold front. Occasional wind gusts
near gale force are possible during this time frame, though whether
or not they will be widespread enough to warrant headlines remains
uncertain. Trends will continue to be monitored through the end of
this week. Periods of showers and storms will accompany the
approaching/passing front, with widespread severe weather not
currently anticipated.

High pressure near 1020 mb will shift from the northern Great Plains
across Lake Michigan Saturday night through Sunday night, bringing
light and variable winds. The next area of low pressure & cold front
will approach from the west early next week, bringing increasing
winds & additional chances for showers and storms. Depending on the
strength of the low and front, periods of gales & some stronger
storms could be possible. Will be providing additional details as
this portion of the period draws closer.

Periods of Small Craft Advisory conditions are possible in nearshore
zones Friday through Saturday, and once again early next week.
Depending on the strength of the surface low pressure center & cold
front responsible for next week's winds, some gales could occur.
Will be monitoring trends for possible headlines from late week into
early next week.

Quigley

&&

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

$$

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