NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 211137
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
637 AM CDT Sat Mar 21 2026

.KEY MESSAGES...

- Patchy fog across southern Wisconsin will slowly diminish
  after sunrise.

- Warm temperatures are expected today across most of the area,
  as gusty southwest winds develop. Highs may rise into the
  lower to middle 70s over most of the area.

- Some chances (around 20 to 30 percent) for light rain to occur
  later Saturday night into Sunday morning, as a cold front
  shifts southward through and south of the area. Cooler
  temperatures and gusty winds are expected.

- Chances (mainly 20 to 30 percent) for precipitation returns to
  the area for middle to later portions of next week.

&&

.UPDATE...
Issued 637 AM CDT Sat Mar 21 2026

Patchy fog across southern Wisconsin will slowly start to burn
off after sunrise this morning. Over the next 30 minutes or so
as temps and winds are at there lowest, the fog will be at its
worst. Overall visibilities are around 4 SM or better so nothing
super noteworthy for a Saturday morning.

As the low pressure system in North Dakota moves east this
morning, a warm front will move across the state. This will be a
dry frontal boundary, but will mark the shift to southwest
winds and start of WAA. There remains small uncertainties in how
warm it will be across southern Wisconsin based on the timing
of the frontal passage. TLDR faster the front moves through the
warmer it becomes and vice versa. Winds should be strong enough
to keep the cooler air from Lake Michigan right along the shore
line to just off shore. So there will be a tight temp gradient
along the lakeshore counties. Not major changes to the forecast.


Patterson

&&

.SHORT TERM...
Issued 1226 AM CDT Sat Mar 21 2026

Overnight through Tuesday:

Patchy fog should linger overnight into early Saturday morning,
as a sharp inversion develops over these areas with a solid
snowpack on the ground. Some dense fog may occur, mainly in low
lying areas. The middle to high clouds that are moving through
may deter some of the fog development. These clouds should move
out of the area by later Saturday morning.

Warm air advection continues into Saturday, as winds shift from
the southeast and south to southwest. Gusty southwest winds
should develop by midday and should push to most of the
lakeshore areas by middle afternoon. Areas toward Port
Washington and Sheboygan may remain onshore until the southwest
winds arrive by 00Z Sunday. This should allow for warm highs
into the lower 70s to reach most of the lakeshore areas, with
lower to middle 70s inland.

A cold front will push south through the area Saturday evening,
with north to northeast winds increasing overnight into Sunday.
Cold air advection will bring cooler temperatures into the area.
A low cloud deck should push southward into the area during
this time as well. There remains some low to mid level
frontogenesis response that shifts southward through the area
during this time.

Forecast soundings remain mixed with the amount of deep
moisture available, so there is uncertainty with how much
precipitation may occur. For now, kept the 20 to 30 percent
chances for light rain later Saturday night into Sunday morning.
A little light snow may mix in on the back end of the
precipitation Sunday morning, though this potential is rather
small (under 20 percent).

High pressure will then move across the region Sunday night and
Monday, then to the east Monday night. South to southwest winds
Tuesday may usher milder temperatures back into the area with
some warm air advection.

Wood

&&

.LONG TERM...
Issued 1226 AM CDT Sat Mar 21 2026

Tuesday night through Friday night:

Synopsis: Modestly cooler conditions will prevail Wednesday
afternoon behind a late Tuesday/Tuesday night frontal passage.
Significantly colder conditions continue to appear unlikely,
with winds shifting out of the southeast by the afternoon hours.
Loose consensus amongst the global ensemble suite suggests that
broad low pressure will develop in the Central Plains Wednesday
afternoon and night, with surface pressure falls elongating
across the eastern half of the CONUS through Thursday night.

Said surface evolution thus continues to put a cold front on
track to move through the western Great Lakes during the day
Thursday. Precip chances return to the forecast Wednesday night
into Thursday along and ahead of the front. Global guidance
suggests that seasonably strong high pressure will settle into
the western Great Lakes Thursday night through Friday night
behind the departed front, resulting in a more noticeable cool
down at the end of next week.

Wednesday Night into Thursday: Precip chances return to the
forecast along and ahead of a passing cold front. Could see
precipitation focus along pre-frontal warm advection Wednesday
evening/night, with chances continuing into the day Thursday as
the passing surface boundary. Current temperature forecasts and
probabilistic p-type forecasts continue to point toward all
rain, with trends continuing to be monitored in coming updates.

Initial forecasts from the LREF suggest that instability for
convection will remain largely south of the region, which is the
likely outcome if the surface progression currently projected
by the ECMWF and Canadian ensemble systems verifies. It is
worth noting, however, that the GEFS presents a deeper and more
northeast progression of surface low pressure, which would open
the door for a slower frontal passage and more time for
instability to build into southern Wisconsin. Will be treating
this solution as an outlier for the time being and leaving any
thunder mentions out of the forecast, but will be watching for
any changes over coming updates.

Quigley

&&

.AVIATION...
Issued 637 AM CDT Sat Mar 21 2026

Patchy fog this morning will bring VFR to MVFR conditions, which
should improve shortly after sunrise. MVFR visibilities of 4 to
5 SM will be few and far between.

Light and variable winds this morning will pick up and become
due southerly for a few hours ahead of an approaching warm
front. As this front passes winds will shift to southwesterly
and become breezy. This front is expected to pass late this
morning into early this afternoon. Dry and breezy conditions
remain through this evening.

A cold front will pass tonight into Sunday morning bringing MVFR
to IFR conditions. Ceilings will drop to around 1-3 kft ahead of
the cold front and will move from north to south. There is a
small chance (10 to 25%) for some light rain with this cold
front. The better chances will be across eastern Wisconsin. The
chances for rain diminishes as you head west. Winds will shift
to the north to northeast behind this cold front at the end of
the period. Rain may linger into the late morning.

Patterson

&&

.MARINE...
Issued 1226 AM CDT Sat Mar 21 2026

Winds will become light overnight, as high pressure around 30.3
inches builds in from Ontario. The high will move east into
Saturday, allowing winds to shift southeast to south. Low
pressure around 29.5 inches developing in eastern Wyoming
Saturday morning will move east southeast Saturday night to the
south of Lake Michigan. This will allow southwest winds to shift
to the north and northeast and become gusty later Saturday
night into Sunday morning.

Gusty southwest winds this afternoon and early evening may reach
Small Craft Advisory levels for the nearshore waters.

The low should move across central Illinois into Indiana Sunday,
as it deepens to around 29.4 inches. A few northerly gales are
possible Sunday, mainly over southern portions of the lake.
Gusty north to northeast winds and building waves will likely
reach Small Craft Advisory levels Sunday into Monday morning.

High pressure around 30.4 inches should then bring decreasing
winds for Monday.

Wood

&&

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

$$

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