NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 181020
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
520 AM CDT Wed Mar 18 2026

.KEY MESSAGES...

- Light powdery snow is exiting from west to east and push out
  over Lake Michigan by 8-9 AM. Patchy slicks spots are still
  possible, especially on elevated and untreated roads.

- 50 percent chance for light rain Wednesday night but could
  linger into Thursday morning. A very brief period of freezing
  rain will be possible over east central WI late Wednesday
  night.

- A warming trend is expected from Wednesday into Saturday.


&&

.UPDATE...
Issued 520 AM CDT Wed Mar 18 2026

Light powdery snow is exiting southern WI this morning. Have
not seen ASOS/AWOS obs pick up on the freezing drizzle on the
backside of the snow that we saw upstream in MN. However, could
not rule out still seeing a brief (less than an hour) of it
mixing in as the snow exits. Overall, patchy slick spots
possible, but mostly limited to elevated and untreated roads.

Otherwise, expect temps to gradually warm above freezing into
the upper 30s to around 40F by this afternoon. However, the
deep snowpack will limit temps, but still should begin to see
some of it gradually begin to melt.

Wagner

&&

.SHORT TERM...
Issued 1200 AM CDT Tue Mar 17 2026

Today through Wednesday:

The snow is finally starting to eat away at the dry air this
evening. Snow has started across western and west central
Wisconsin. Virga may still be the winning out in the east but
now that switch has flipped to a saturated low level that too
should progress nice across the entire area. If you haven't seen
snow by now then it should arrive around Midnight or shortly
thereafter. This will be a dry and powdery snow. Rates will be
low and overall accumulations of snow are around 1 inch. Far
southwestern portions of the area could see up to 2 inches and
areas in our northeast could see around a half an inch.

Looking later into the morning, mid level WAA continues to
slowly cause temperatures to rise above zero. Some sounding
models are still trending with this layer losing saturation in
the mid levels but the result is still the same. Whether we lose
saturation aloft or warm above zero, the low levels are still
saturated below freezing and that will result in a loss of cloud
ice. This will give us a small window for freezing drizzle. This
further tracks with whats up stream in on the western edge of
this system in Iowa and Minnesota. The earliest we could see in
this in our west is around 2 AM and that would slowly pull east
until it exits around 8 AM. This will be a very fine
drizzle/mist so not anticipating more than a glaze of ice
possible.

Skies will remain mostly to partly cloudy through the rest of
the day once the snow and freezing drizzle has ended. Clouds
from this system will pull out as those from the next incoming
system for tonight move in. The set up will be very similar with
this next system however, temperatures will be warmer under the
persistent south to southwest winds and WAA. Therefore the
predominate precipitation type will be rain. Light rain showers
should move in late this evening into tonight and persist into
late Thursday morning. Meso models do have two distinct areas of
precipitation which shows the spread well here. One has rain
mostly along and east of Marquette to Dodge to Kenosha Counties
while the other option is more along a line from Sauk to Dane,
to Rock. Everyone should see rain at some point, but there will
be a narrow area that gets 0.1 to 0.2 inches of rain. Kept POPs
broad across the area as this could fluctuate yet on who sees
it, but this will largely be unimpactful. Whats more impactful
is the concern that we get fog as well during this time.
Temperatures will be slightly warmer, snow will be melting and
light and variable. If fog does develop it will likely remain
into Thursday morning or beyond high pressure builds in keeping
winds light and melting snow keeps the low level saturated.

Patterson

&&

.LONG TERM...
Issued 1200 AM CDT Tue Mar 17 2026

Thursday through Monday:

An upper level ridge will begin to slowly shift east out of the
western CONUS Thursday. As this ridging builds in there are signs
for a shortwave trough to move through the larger flow late Thursday
night into Friday, but guidance is slowly lifting that shortwave
further north. This is keeping the better PVA across northern WI,
Michigan and Canada. Thus chances for precipitation are very low
to near zero across southern Wisconsin. Sheboygan CO is the only
area to get around 10% Friday late morning/afternoon as this
shortwave pulls out to the east. South to southwest winds and
warming temperatures will favor rain should this system pull
slightly south in subsequent runs.

As the shortwave clears the ridge will remain until late Saturday
and Sunday. Guidance is suggesting a stronger trough descending
across the Pacific Northwest and advecting east. This would
flatten out the ridge across the entire Northern Plains and into
the Great Lakes Region for the weekend. While the overall
consciouses of flatting the ridge is flavored, the time that
this occurs and the strength of the trough differs greatly. This
is most easily seen the deterministic guidance, but shows up in
the ensembles and cluster analysis as well. The cluster
analysis is highlight the ridge with a monopole structure
showing the spread in the strength and amplitude over the
trough, but the signal remains on how much this breaks down.
From deterministic guidance, the Euro is the fastest with the
trough favoring a more northern track. While the GFS and CAN are
slower and slightly further south with the 500 mb PVA. This
translates with the low POPs around 10-20% Saturday night
through Sunday. That should be refined as we get closer to the
weekend.

One more exciting feature if your looking forward to warm weather
this spring is that the upper level ridging and low pressure
systems passing to our north will bring WI some WAA. South to
southwest winds will set up Friday and remain largely in place
through Sunday morning. This will bring in some slightly above
normal temperatures. Saturday looks to be the warmest by far, but
there could be further adjustments in how warm it gets. Guidance
tends to struggle with temperatures in the spring and fall.
Wouldn't be surprised to see some slightly colder temperatures if
the snowpack is still lingering around (still warm but maybe not
in the mid to upper 60s like some of the ensemble guidance is
suggesting). Only time will tell. Beyond this weekend, weather is
largely uneventful with high pressure moving through the Great
Lakes Region and a return to normal temperatures.

Patterson

&&

.AVIATION...
Issued 520 AM CDT Wed Mar 18 2026

Last of the light snow will continue to push east this morning.
While obs have not shown the freezing drizzle materialize,
still cannot rule out a brief, less than hour window of it
mixing in as the snow departs. Otherwise, MVFR ceilings are
looking to linger behind the snow for a couple of hours, but
expected to lift later this morning into the afternoon. Modest
southwest winds will prevail this afternoon before becoming
light and variable this evening with VFR conditions. Still
looking at another round of precipitation overnight into
Thursday morning. Generally tanking much of the area will see
rain with this activity but for east-central WI terminals,
cannot rule out pockets of freezing rain at times. Overall, the
potential is there for some minor icing concerns overnight, but
uncertainty on locations and impacts remains.


Wagner

&&

.MARINE...
Issued 12:00 AM CDT Tue Mar 17 2026

Light to moderate southwest to south winds are expected across
the lake as high pressure around 30.2 inches moves east north east from
southern Illinois toward the southern New England States. a
Modest to breezy southwest winds will prevail into tonight as
low pressure of 29.7 inches progresses through the southern
Canadian Prairies into Ontario. A weak cold front will then
slowly pass Thursday into Thursday evening with light and
variable winds.

A Small Craft Advisory is in effect for the nearshore waters
this morning into early this evening due to the breezy south-southwest
winds and building waves.

Patterson

&&

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

&&

$$

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