NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 181857
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
157 PM CDT Wed Mar 18 2026

.KEY MESSAGES...

- A mix of freezing rain and rain will be possible overnight
  tonight into early Thursday morning, which could result in
  some slick spots for the Thursday morning commute. At this
  time, confidence is not high in the development of
  precipitation and resultant icing impacts, but this remains
  worth keeping an eye on.

- A gradually warming trend is expected through the remainder
  of the week

&&

.SHORT TERM...
Issued 157 PM CDT Wed Mar 18 2026

Tonight and Thursday:

Warm advection aloft will persist through the remainder of today
and into tonight. Clouds associated with the departing system
continue to gradually decrease from the southwest, with a
period of mostly clear skies possible later this afternoon into
the evening. Best chance for clearing is across the southwest
half of the forecast area. Despite the warm air advection
aloft, the clearing skies and light winds along with the
widespread snow pack may lead to temps falling a good amount
through the evening hours (especially southwest areas), before
clouds associated with approaching shortwave put a damper on any
radiational cooling. Could also see some fog develop tonight,
mainly across the southwest half of the forecast area where
there is a better chance for prolonged mostly clear conditions.

The big concern tonight is whether there will be enough moisture
in the low and mid levels for period of measurable precip as
the shortwave moves through. The 12Z GEFS mean probability for
at least 0.01" liquid is less than 10% for most of the forecast
area tonight, with 10-30% in the far northeast. The NAM is
similarly dry, though a couple of the 12Z CAMs are relatively
bullish with a band of precip dropping southward through the
area the second half of the night into early Thursday morning.
If precip does indeed develop, there is a concern for a round of
freezing rain given the potential for colder surface temps in
place at the onset of the precip. Limited the higher precip
chances (40-60%) and totals towards the northeast based on the
bulk of 12Z guidance, with lower chances (20-30%) in the
southwest.

There is also some question about temps tonight across the
northeast half of the forecast area, as any lingering clouds
might result in temps right near or slightly above freezing.
Could see a mix of rain and freezing rain in these areas if
precip does develop. Given the overall uncertainty with this
system, will be holding off on an Winter Weather Advisory for
freezing rain for now. Cloud trends into this evening as well as
the development of precip upstream over the next few hours
should better clarify the potential for local impacts overnight.

Clouds may linger much of the day tomorrow, with light easterly
winds expected. Even though temps aloft will be fairly mild,
these conditions along with the lingering snow pack will likely
keep surface temps from warming that much. Kept highs towards
the lower end of guidance and could still be a degree or two too
mild.


DDV

&&

.LONG TERM...
Issued 157 PM CDT Wed Mar 18 2026

Thursday night through Wednesday:

Low pressure is expected to pass by to the north Thursday night,
dragging a cold front through southern Wisconsin by early to mid
morning Friday. This system generally looks dry for the forecast
area. Confidence is not great in high temps for tomorrow given
the tight temperatures gradient across the region in addition to
the front dropping through. Could end up seeing highs several
degrees cooler than currently forecast given a faster cold
front (as models seem to be trending towards).

The frontal boundary is expected to lift back through the region
as a warm front on Saturday ahead of an approaching low. There
is a question as to how far north the front will make it, with
the 12Z NAM and Canadian solutions suggesting the front will
struggle to make it far into the forecast area (if at all). The
12Z GFS and ECMWF solutions continue to suggest the front will
make it all the way through southern Wisconsin, resulting in a
mild day under south to southwest winds. The chilly waters of
Lake Michigan often beat back a warm front this time of the
year though, so wouldn't be surprised to see the front struggle
per the prior mentioned models. The latest forecast does keep
somewhat cooler temps in the northeast, with the best chance for
above normal temps from Madison southwestward.

The frontal boundary will likely have shifted back south of the
WI/IL border by daybreak Sunday, with cooler conditions likely
across southern Wisconsin. Even cooler temps are expected Monday
as high pressure slides into the area from the northwest. Temps
are expected to moderate back towards or even a bit above normal
by mid-week.

DDV

&&

.AVIATION...
Issued 157 PM CDT Wed Mar 18 2026

Low clouds continue to generally decrease in coverage from the
southwest this afternoon, with a back edge around the Eau Claire
area also approaching from the northwest. Thus there remains a
chance for some continued clearing late this afternoon into the
evening.

A shortwave will bring some rain and freezing rain chances to
the area tonight into early Thursday morning. There remains a
lot of uncertainty as to whether the precip will impact southern
Wisconsin, as models have been generally trending drier and
farther north with the precip over the last 24 hours. Opted to
keep PROB30 mentions for rain and freezing rain in the TAFs for
now given the uncertainty. Upstream precip trends over the next
few hours along with short term model runs will hopefully bring
a bit more clarity to the forecast.

There is the potential for some fog tonight, particularly
within areas of clearing given light winds expected. Low clouds
are likely to return as well as the shortwave moves through,
with lingering clouds possible across at least the northern half
of the forecast area on Thursday.

DDV

&&

.MARINE...
Issued 157 PM CDT Wed Mar 18 2026

Breezy south to southwest winds will continue through late
afternoon as low pressure of 29.8 inches pass by north of Lake
Michigan. The current 5 pm CDT expiration time of the Small
Craft Advisory still looks good based on latest expected winds
and waves. High pressure of 30.2 inches will then move overhead
tonight and Thursday, bringing lighter winds to the lake. Light
to moderate south to southwest winds are then expected Thursday
night into early Friday ahead of a cold front, with winds
becoming northerly through the day Friday as the front drops
through the area. Breezy southerly winds are expected Saturday
ahead of an approaching low, with gusty northerly winds likely
Sunday behind the low and associated cold front.

DDV

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 5 PM
     Wednesday.

&&

$$

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