969
FXUS63 KGRB 090459
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1059 PM CST Mon Dec 8 2025

Updated aviation portion for 06Z TAF issuance

.UPDATE...
Issued at 834 PM CST Mon Dec 8 2025

Took a closer look at tonight`s system, as well as the stronger
system for Tuesday night.

Tonight`s system appears to be on track to produce 1-3 inches of
snow. The main change was to add a bit more areal coverage of
freezing drizzle as the snow ends and moisture shallows out
in central and east central WI late tonight into Tuesday morning.
Don`t think the freezing drizzle will result in additional travel
concerns, as any very light ice accumulations will be falling on
snow covered roads.

Tuesday night`s system continues to be a problem, as surface low
tracks range from southern WI (ECMWF/GFS) to northern WI (latest
RAP/HRRR), with most other models taking the low through central
WI. This leads to significant differences in the position of the
axis of max snowfall, and opens the possibility for warmer air and
a mix with rain in central and east central WI (with the northern
solutions). There is also the issue of whether or not we`ll see
heavy snow, as earlier probabilistic forecasts were only showing
a 30-50 percent chance of 6+ inches. So, with so many question
marks, the plan is to leave the current watch in place and let the
midnight crew digest the full 00z model suite and make any
necessary headline adjustments. The only changes made to the
Winter Storm Watch earlier were to back off on blowing snow
wording in eastern WI due to an expected wetter/denser snow, and
adding a mention of possible sporadic tree damage and power
outages.

&&

.KEY MESSAGES...

- A clipper system is expected to bring a swath of 1 to 3 inches
  of snow across the area tonight. Highest amounts across far
  northern Wisconsin.

- A more potent clipper system is expected to bring another round
  of snow to the area late Tuesday afternoon into Wednesday
  morning. This system is expected to produce 3-5 inches of snow
  over much of the forecast area, with a narrow band of higher
  amounts closer to 6 to 7 inches. A Winter Storm Watch is in
  effect for the southern two-thirds of the forecast area.

- Much colder temperatures arrive for the end of the week. Wind
  chills of -10 to -30 are possible Friday night into early
  Saturday and again Saturday night into Sunday morning.

&&

.DISCUSSION...
Issued at 349 PM CST Mon Dec 8 2025

Short Term...Tonight and Tuesday

Ahead of an approaching clipper system, low-level moisture moved
into the area bringing low-level clouds and flurries to central
and north-central WI this afternoon. Southerly winds have also
allowed for low-level moisture/clouds to move inland from Lake MI
resulting in scattered flurries across eastern WI this afternoon.
These conditions are expected to continue until the aforementioned
clipper system moves into the area this evening and overnight.

While not very strong, this clipper system will spread snow
across the region from west to east from late this evening and
taper off/end by early Tuesday morning. By Tuesday morning,
snowfall amounts of 1 to 3 inches are expected across the entire
forecast area. The higher snowfall amounts are anticipated across
far northern WI where the better forcing will be located. While
there may be minor travel impacts to the Tuesday morning commute
on untreated/secondary roads, there is also potential for a brief
period of freezing drizzle Tuesday morning, as forecast soundings
indicate the loss of ice crystals aloft as the snow is ending.
Therefore, a few spots may become slick Tuesday morning following
the departure of the snow. Additionally, gusty southerly winds
will accompany the clipper system with gusts to 20 to 25 mph,
which will cause reduced visibility at times while the snow is
falling.

There will be a lull in precipitation and winds late Tuesday
morning through the late afternoon before the next clipper
system arrives. During this time, a few breaks in the clouds are
possible as high temperatures climb into the mid 20s to low 30s.
The next clipper system will arrive from the west late Tuesday
afternoon into the evening, bringing the chance for several inches
of snow. For more details, see the long term discussion.

Long Term...Tuesday Night Through Monday

The main focus for the extended will be a passing clipper system
Tuesday night into Wednesday followed by much colder air
temperatures around the end of the week.

Snow Tuesday into Wednesday...
A strong clipper system is expected to cross into Wisconsin
Tuesday, bringing accumulating snowfall late Tuesday afternoon and
Tuesday evening. The timing/location for the heaviest snowfall
will likely be Tuesday evening in an area just north and east of
the upper low Tuesday evening, but this will likely be a
relatively narrow band compared to the overall snowfall. As a
result a widespread 3-4 inches seems likely with a narrower band
getting closer to 5-7 inches. As model certainty remains low on
the location of this higher band, maintained the watch over the
region this forecast issuance. Would expect the current Winter
Storm Watch covers more counties than will ultimately see a
warning, given the above info. On the backside of this system
Wednesday, expect strong cold air advection to continue snowfall
into Wednesday morning and stronger winds by the late morning to
afternoon period. Wind gusts up to 20 to 30 mph at times will
allow for some drifting snow in open areas during the day
Wednesday. Drier air will ultimately bring an end to the snow for
most Wednesday afternoon.

Cold...
Much colder air moves in behind this system, starting Wednesday
night through the early weekend. Overnight low temperatures will
see a downward trend from a few degrees above zero Wednesday night
to below zero across the whole area Friday and Saturday night.
Saturday high temperatures are expected to only be a few degrees
above zero for much of the area. Wind chills in the coldest parts
of the weekend may also reach as low as -10F to -30F at times.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1051 PM CST Mon Dec 8 2025

Snow was just starting to develop over NC/C WI late this evening,
and should be approaching the eastern TAF sites shortly after
issuance time. This quick-moving clipper system will bring
accumulating snowfall, reduced vsbys, and widespread IFR
conditions to the area through the overnight hours. By early
Tuesday morning, 1-3 inches of snow is forecast over the area,
with the highest amounts expected along and north of Hwy 29. As
the snow ends late tonight/early Tuesday, a period of light
freezing drizzle and IFR conditions may occur for several hours,
especially in central and east central WI. A gradual improvement
in flight conditions is expected during the late morning and
afternoon, though light snow is poised to return to central WI
(including AUW/CWA) late in the afternoon. Widespread snow will
overspread the area Tuesday evening as a strong low pressure
system arrives. There are still some significant model differences
with this system, so the location of the heaviest snow band is in
question.

Southerly winds will continue overnight with gusts to 15 to 20
kts. A period of LLWS is expected at AUW/CWA/GRB/ATW into the
overnight hours, with southwest winds of 35 to 40 kts just above
the surface. Surface winds will turn westerly late tonight into
early Tuesday, then eventually become east to southeast Tuesday
evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Tuesday afternoon through late Tuesday
night for WIZ018>021-030-031-035>037-045.

Winter Storm Watch from Tuesday evening through Wednesday
morning for WIZ022-038>040-048>050-074.
&&

$$

UPDATE.........Kieckbusch
DISCUSSION.....Kruk/Uhlmann
AVIATION.......Kieckbusch

NWS GRB Office Area Forecast Discussion