721
FXUS63 KMKX 070354 AAA
AFDMKX

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

.KEY MESSAGES...

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

- 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.

&&

.UPDATE...
Issued 954 PM CST Sat Dec 6 2025

No changes to the current Winter Weather Advisory headlines for
now from Sauk to Milwaukee County and south overnight into early
Sunday morning.

The light to moderate snow continues to steadily push east into
the area, and should reach the lakeshore areas between 11 PM and
midnight CST. This system continues to be driven by strong 850
mb frontogenesis response and the approaching 500 mb shortwave
trough from the west. There is some warm air advection in the
low levels also helping with the upward vertical motion. These
features will move east through the area overnight and exit to
the east early Sunday morning.

The snowfall rates should be around 1/2 inch per hour in
southern portions of the area, with rates 3/4 to perhaps 1 inch
per hour in the far south near the Illinois border, where the
best frontogenesis response may occur.

Total snowfall amounts look to range from 2 to 5 inches in the
advisory areas, with 1 to 2 inches to the north of there. There
may be some lake enhancement in far southeast Wisconsin near the
lake, which may bring some 6 inch amounts there. In addition,
some 6 inch amounts may occur southwest of Madison, closest to
the stronger 850 mb frontogenesis response.

There is some possibility for the 2 to 5 inch amounts to remain
over the southern half of the area, so Sauk County may see a
little less than forecast. For now, will leave them in the
Advisory and see if the heavier bands remain to the south of
there overnight.

The snow character is expected to remain rather fluffy, with
snow to liquid ratios of 12 to 1 to 15 to 1 anticipated. The
main impacts remain snow covered and slippery roads for
overnight into early Sunday morning.

Wood

&&

.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 954 PM CST Sat Dec 6 2025

The light to moderate snow continues to steadily push east into
the area, and should reach the terminals near Lake Michigan
between 05Z and 06Z Sunday. The snow will move east through the
area overnight and exit to the east early Sunday morning.

The snowfall rates should be around 1/2 inch per hour for
terminals in southern portions of the area, with rates 3/4 to
perhaps 1 inch per hour for terminals near the Illinois border.

Total snowfall amounts look to range from 2 to 5 inches for the
southern terminals, with 1 to 2 inches to the north. There may
be some lake enhancement for Milwaukee and Kenosha, which may
bring some 6 inch amounts there. In addition, some 6 inch
amounts may occur southwest of Madison. The snow character is
expected to remain rather fluffy.

Ceilings should drop to 1000 to 1500 feet AGL in southern
portions of the area with the snow, with 1500 to 2000 feet AGL
ceilings to the north. Visibility should drop to around 1 mile
with the snow as well, with 3/4 to 1/2 mile values possible at
times for terminals near the Illinois border.

Light northeast winds will become north overnight into Sunday
morning, increasing Sunday afternoon and becoming gusty at
times. Winds will become light again Sunday night, possibly
shifting northeast for terminals near the lake.

There is a small chance for lake effect snow showers Sunday
night for the lakeshore terminals, though confidence in this
occurring is low at this time.

Wood

&&

.MARINE...
Issued 954 PM CST Sat Dec 6 2025

Winds will increase and become north to northwest overnight
into Sunday, as low pressure around 29.9 inches crosses central
Illinois and Indiana. High pressure around 30.5 inches will also
build into the Upper Midwest. A Small Craft Advisory is in
effect for the nearshore waters south of Port Washington Sunday
into early Monday morning.

Winds will shift to the south Monday afternoon, as low pressure
around 30.0 inches passes north of Lake Superior. Another low
around 29.7 inches will track from Minnesota to Sault Ste. Marie
Monday night through Tuesday morning. A period of southerly
gales up to 35 knots is looking more likely during this time for
the open waters of Lake Michigan, with gusts up to 40 knots
possible over far northern open waters.

The next low around 29.1 inches will track across central
Wisconsin Tuesday night and reach southern Ontario by midday
Wednesday. Gales are possible for the south half of the lake
during this time.

A Small Craft Advisory will be needed for all of the nearshore
waters Monday night through Wednesday night, with a few gale
force gusts possible.

MRC/Wood

&&

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

     Winter Weather Advisory...WIZ064-WIZ065-WIZ066-WIZ070-WIZ071-
     WIZ072 until 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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