NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 062117
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
317 PM CST Sat Dec 6 2025

.KEY MESSAGES...

- Widespread accumulating snowfall this evening into early
  Sunday. Snow totals of 1 to 3 inches north of I-90/I-94 and 3
  to 5 inches along and south. Localized totals around 6 inches
  are possible in far southwestern and far southeastern
  Wisconsin. A Winter Weather Advisory is in effect for Sauk
  County to Milwaukee County and southward.

- Additional rounds of snowfall will be possible again Monday
  night into Tuesday and Tuesday night into Wednesday. Tuesday
  temperatures will likely rise above freezing, which means
  snow may start as rain.

- Additional rounds of snowfall are then possible through the
  end of the work week, but confidence in timing is much lower.

- Below normal temperatures continue through next weekend.

&&

.SHORT TERM...
Issued 317 PM CST Sat Dec 6 2025

Tonight through Sunday night:

The clipper system tracking into southern Wisconsin tonight has
taken shape across western Iowa and southwestern Minnesota this
afternoon, with the strongest precipitation/frontogenesis area
developing over central to northern Iowa. This lends credence to
the southward shift of the mesoscale modeling that indicates the
majority of QPF will fall across the southern two tiers of
Wisconsin counties, but some individual models still indicate
potential for a band of heavier precipitation in the Wisconsin
River Valley, so for now will let Sauk County remain in the
Winter Weather Advisory (currently covering Sauk County to
Milwaukee County and all areas southward). Deep dendritic
growth zones are noted in the soundings from the Wisconsin River
Valley, so even with a shorter period of precipitation rates
may reach near 1"/hr and create hazardous travel conditions.

These 1"/hr rates are also possible in banded precipitation
near the WI/IL border, where precipitation also lasts longer,
and in far southeastern Wisconsin where some lake enhancement is
possible as winds turn northeasterly. Therefore, local
accumulations up to 6 inches are possible along the border
regions. Elsewhere within the Winter Weather Advisory, expect
accumulations of 2 to 5 inches.

Precipitation will taper off into Sunday morning, with skies
expected to clear through the day as arctic high pressure pushes
in with northerly winds. Expect highs in the upper teens. Winds
shift to northeasterly overnight Sunday, potentially bringing a
diffuse band of lake effect snow slightly onshore. Not
anticipating any strong banding or significant accumulations at
this time (~20 percent chance of precipitation). Lows around
zero degrees are expected across inland regions, with areas east
of the Kettle Moraine slightly higher in the 5 to 15 degree
range.

MH

&&

.LONG TERM...
Issued 317 PM CST Sat Dec 6 2025

Monday through Saturday:

A lake effect snow band may brush southeast WI Monday morning
before getting pushed into the north half of the lake by
increasing southerly winds during the afternoon. High temperatures
will reach the lower 20s and we can expect mostly cloudy skies.

A shortwave trough will track across WI during the day Monday,
but the weak lift from vorticity and warm air advection (and dry
low levels) should keep precip confined to central and northern WI
during the afternoon.

A more robust shortwave trough will progress through central and
northern WI Monday night into Tuesday morning. Broad low and mid
level lift ahead of and along this wave will bring widespread,
light snow to WI. Despite the likelihood of seeing snow (50-65%
north of I-94 and 30-50% south), it only looks like around a half
inch near Fond du Lac and Sheboygan, and trace amounts near the IL
border.

Snow should exit by mid Tuesday morning. The next surface low in
response to a stronger mid level shortwave trough will track from
Saskatchewan to west central MN on Tuesday and across central WI
Tuesday night. The 12Z runs of the ECMWF and GFS have come into
better agreement on the track of the low, but there is still some
uncertainty.

The big challenge with this Tuesday night event will be the precip
type for southern WI. We will begin above freezing Tuesday
afternoon in the warm sector and then likely remain in that warm
sector if the low tracks across central WI. With loss of daylight,
temps will probably sink just below freezing, but the temps aloft
(925-850mb) should be in the 0-2C range south of the low. As long
as we have deep enough saturation into the snow growth zone, then
snow will be the primary ptype. But if we lose ice crystals, a
wintry mix could occur. These are the details that will need to
get hashed out as we get closer to the event.

Another arctic blast will move in behind that low. Gusty northwest
winds are expected Wednesday afternoon, and lows will drop into
the single digits for most areas Wednesday night. We could also
see scattered light snow showers.

A swath of snow is expected to fall across the Midwest on
Thursday. There are still big differences in the forecast
location due to uncertainty in the amplification of the mid level
shortwave trough. Some models clip far southern WI with the snow
and others miss us all together. And... there is yet another
chance for snow next weekend.

Cronce

&&

.AVIATION...
Issued 317 PM CST Sat Dec 6 2025

A deck of MVFR clouds is maintaining its hold on far southern
Wisconsin, while a main deck around 3200 ft is slowly overtaking
the rest of southern Wisconsin this afternoon ahead of the snow
system tonight. Initial rounds of flurries and light snow are
expected to maintain VFR conditions, but expecting ceilings to
rapidly fall to 1000-1900 ft as heavier snow moves in late this
evening into tonight. The heaviest snow is expected along the
WI/IL border, bringing visibilities down to 1/2 mile in some
places and ceilings down to IFR. Snow will taper off from west
to east early Sunday morning and VFR conditions will prevail
afterwards, although MVFR ceilings will likely linger along
Lake Michigan terminals through late morning/early afternoon.

Expect light and variable winds this afternoon to shift to
northeasterly overnight and to northerly into Sunday. Gusts of
15 to 20 kt are expected throughout Sunday, with winds
diminishing Sunday night.

MH

&&

.MARINE...
Issued 317 PM CST Sat Dec 6 2025

Winds will become northerly tonight into Sunday and increase as
low pressure crosses central Illinois and Indiana and high
pressure builds into the Upper Midwest. A Small Craft Advisory is
in effect for gusts up to 25 kt and high waves of 4 to 6 feet.

Winds will shift to the south Monday afternoon as low pressure
passes north of Lake Superior. Another stronger low will track
from Minnesota to Sault Ste. Marie Monday night through Tuesday
morning. A period of southerly gales up to 35 kt is looking more
likely during this time, with gusts up to 40 kt possible over far
northern Lake Michigan.

The next low will track across central Wisconsin Tuesday night
and then reach southern Ontario midday Wednesday. Gales are
possible for the south half.

MRC

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory...WIZ056-WIZ062-WIZ063-WIZ067-WIZ068-
     WIZ069...8 PM Saturday to 6 AM Sunday.

     Winter Weather Advisory...WIZ064-WIZ065-WIZ066-WIZ070-WIZ071-
     WIZ072...10 PM Saturday to 8 AM Sunday.

LM...Small Craft Advisory...LMZ644...8 AM Sunday to 9 PM Sunday.

     Small Craft Advisory...LMZ645-LMZ646...8 AM Sunday to 3 AM
     Monday.

&&

$$

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