NWS-Milwaukee/Sullivan Forecast Discussion
FXUS63 KMKX 051145
AFDMKX
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
645 AM CDT Sat Sep 5 2026
.KEY MESSAGES...
- Patchy dense fog across southern WI early this morning,
especially in western Dane county and the Baraboo / Wisconsin
River Valleys.
- Milder temps and drier, less humid conditions this weekend and
Labor Day with daytime highs in the 70s and low 80s and
nightly temps falling into the upper 50s to low 60s.
- Warmer temps and humidity return Tuesday and Wednesday with
the next chances for shower and thunderstorms.
&&
.UPDATE...
Issued 645 AM CDT Sat Sep 5 2026
DOT cameras and surface observing networks reveal some patchy
dense fog across the western MSN beltline and the Baraboo / WI
River Valleys. A few other pockets of fog across the rest of
southern WI, especially in low-lying marshy areas (several
airport observing sites), higher elevation areas (intersecting
the < 300-600 ft overcast cloud ceilings), and the immediate
shoreline of Lake MI. Expecting the fog and low cloud ceilings
to slowly lift over the course of the next few hours, remaining
mostly cloudy until mid-afternoon.
The holiday weekend forecast remains on track. Dry and quiet
weather with lingering humidity today (dewpoints around 70)
followed by slightly less humid conditions Sunday into Monday.
Sheppard
&&
.SHORT TERM...
Issued 1201 AM CDT Sat Sep 5 2026
Today through Sunday night:
Outside of an isolated pop-up shower toward the WI/IL border,
mostly dry into the morning. Otherwise, we continue to see a
weak cold front continue push its way southward through the
morning enhanced by the easterly flow from high pressure. Light
winds and elevated surface moisture from recent rainfall behind
the front will set the stage for fog development across the area
through the morning. Expect pretty widespread coverage with
visibilities of 1-3sm, but also could see pockets of dense fog
at times, especially for low-lying areas and river valleys. Do
not know if and how widespread the dense fog may get, but will
continue to monitor and see if a advisory may be warranted.
Nonetheless, the fog is expected to continue through the
morning, but gradually lift by mid to late morning with some
lower clouds lagging behind by an hour or two.
Expect drier, not as humid, and milder conditions by this afternoon
as upper-level ridge begins to build across the Upper Midwest. This
will allow light easterly flow off of Lake Michigan to become more
prevalent across southern WI as high pressure builds into the Great
Lakes region from Canada through the afternoon and evening. As a
result temps in the upper 70s toward the lake and to lower 80s
inland toward southwestern WI expected this afternoon. Cooler
conditions are expected overnight with lows dipping into the upper
50s to low 60s.
This high pressure and drier pattern will remain in place through
the remainder of the holiday weekend with similar temps
and drier conditions for Sunday along with less humidity.
Wagner
&&
.LONG TERM...
Issued 1201 AM CDT Sat Sep 5 2026
Monday through Friday:
Influence from the upper-level ridge and surface high pressure
over the Great Lakes will continue trough the holiday as it will
be reinforced by an additional area of high pressure building
down. Predominately easterly flow off of Lake Michigan will help
keep a couple of degree cooler than what we have been seeing
along with less humidity. Highs for Labor Day are looking to top
off in the upper 70s to low 80s.
Then influence from the high pressure wanes into Tuesday as the
upper-level ridge axis slides eastward while and upper-level
trough lifts across the Upper Midwest. This pattern shift is
expected to bring more southerly flow to southern WI along with
low-level WAA, moisture advection, and temps warming back into
the 80s for Tuesday into Wednesday. This will also be the next
window for increased shower and storm chances across the area as
it brings a surface low across Manitoba/Ontario with a cold
front drifting across the Upper Midwest later Tuesday into
Wednesday. However, the better upper- level dynamics look to
remain to the north closer tied to the trough/low itself, the
low-level forcing from the front along with some WAA and signs
of a LLJ are looking to be enough for the increased PoP chances
later Tuesday into Wednesday.
Then behind the midweek system, the pattern is trending more
benign with zonal upper-level flow and high pressure building
across the region for the end of the week.
Wagner
&&
.AVIATION...
Issued 630 AM CDT Sat Sep 5 2026
Overcast low cloud ceilings and patchy dense fog are leading to
widespread LIFR conditions early this morning. Expecting these
ceilings to slowly lift to IFR / Fuel-alt MVFR levels later this
morning and scatter apart to VFR through this afternoon. Skies
then remain mostly clear through the rest of the TAF period as
high pressure builds into the region. Northeast winds at 5 to
10 knots today, light and variable late tonight, then light
easterly winds for Sunday. Dry weather expected through the TAF
period and the rest of the holiday weekend.
Sheppard
&&
.MARINE...
Issued 1201 AM CDT Sat Sep 5 2026
Light winds over Lake Michigan will shift east-northeasterly
overnight into Saturday morning a cold front gradually slides
southward. Areas of dense fog may form over central and
southern Lake Michigan after the frontal passage and continue
through Saturday morning. Then high pressure builds over the
Great Lakes from Ontario through the weekend and will bring
modest northeast winds through Saturday, especially for central
and southern Lake Michigan. Winds eventually weaken and become
more light and variable for Sunday and Monday as an additional
high pressure slowly reinforces the high pressure over the Great
Lakes.
Wagner
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&
$$
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