NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 120505
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1105 PM CST Thu Dec 11 2025

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- A band of light snow will bring accumulations less than an inch
  to the area on Friday. The snow may result in locally slick
  travel.

- Bitterly cold this weekend. Daytime highs will struggle to reach
  zero over much of central WI on Saturday. Confidence is high
  that wind chills will fall as low as 20 below to 30 below zero
  Friday night as well as Saturday night. Cold weather headlines
  will be needed.

- A rapid warming trend is expected early next week, with
  temperatures recovering into the 30s by Tuesday.

&&

.DISCUSSION...
Issued at 212 PM CST Thu Dec 11 2025

The latest RAP analysis and satellite imagery show high pressure
stretching across western Wisconsin and western Lake Superior
early this afternoon. Northwest winds on the periphery of this
high continue to advect low-level moisture and clouds into far
north-central and eastern Wisconsin, with some flurries reported
over Vilas County at times. Upstream, additional mid and high
clouds are streaming into the region ahead of weak shortwave
impulses located over northwest Minnesota and southern
Saskatchewan. The Saskatchewan shortwave is driving a potent
arctic front southeast, which is currently forecast to arrive in
northeast Wisconsin on Friday.

Forecast concerns mainly revolve around cloud trends and temperatures
tonight, followed by light snow potential and the subsequent arctic
outbreak on Friday through Sunday.

Short Term...Tonight and Friday

High pressure will slide southeast across the area tonight. While light
northwest flow will continue off Lake Superior this evening, trajectories
are expected to back to the west overnight. This shift may allow for some
movement or erosion of the lingering low stratus. Cloud cover may be slow
to dissipate in some areas, complicating the temperature forecast.
Meanwhile, some guidance suggests fog developing over the Fox Valley after
midnight. Given the light winds and potential for partially clear skies,
patchy development is supported, but the lack of widespread fog earlier
this morning suggests this may not be a significant impact.

Attention then turns to the arrival of the arctic front on Friday.
Shortwave energy will push this feature across the region, accompanied by a
band of light snow. Precipitation is expected to arrive in north-central
Wisconsin between 8 am and 9 am, spreading into northeast Wisconsin by
around 12 pm. Forecast soundings indicate weak to moderate lift within a
dendritic growth zone approximately 150 mb thick, which should support the
development of light, possibly fluffy snow. Accumulations of a half inch to
one inch will be possible over north-central Wisconsin, while most other
locations will see a half inch or less. The snow is expected to exit the
area by the end of the afternoon. Behind the front, west-northwest winds
will increase late in the day, with gusts to 25 mph possible. This could
cause very minor blowing of any new, fluffy snow.

Long Term...Friday Night through Thursday

Behind the clipper system, a relatively quick round of bitter cold air remains
on track for the weekend. 850mb temperatures are forecast to fall to around
15 degrees Celsius below normal. Confidence is high that wind chills will
plummet to between 20 below and 30 below zero late Friday night into
Saturday morning across most of the area. A few locations may
flirt with 35 below over north-central WI.  Door County and
possibly Marinette County may see slightly less severe values, in
the 10 below to 20 below zero range. The current forecast places
wind chills below the 25th percentile of guidance, indicating a
solution on the colder side of the envelope. A Cold Weather
Advisory looks likely for this period and most of the area.

After a brief moderation on Saturday afternoon, wind chills will approach
advisory criteria once again on Saturday night. Veering low-level flow is
expected to bring increased cloud cover to far northern Wisconsin, which
lowers confidence in advisory-level cold for that specific area compared to
Friday night. However, central Wisconsin will have the highest probability
of reaching advisory criteria due to higher confidence in clear skies,
allowing wind chills to potentially reach 30 below zero.

The core of the bitter cold airmass will begin to depart on Sunday, giving
way to a rapid warming trend early next week. Temperatures will return to
the teens and 20s on Monday, reaching the lower 30s by Tuesday. In terms of
precipitation, indications suggest weak clipper activity could bring
chances for light snow in a warm advection pattern to far northeast
Wisconsin on Monday and Tuesday, though confidence in wintry impacts
remains low. Confidence is slightly higher for precipitation chances late
Tuesday night into Wednesday associated with a cold front. Medium-range
models are hinting at a more dynamic system crossing the region late
Wednesday night into Thursday, which will bear watching in future forecasts.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1053 PM CST Thu Dec 11 2025

Stratus still covered much of the northeast half of the forecast
area late this evening, and was gradually filling back in over the
Fox Valley. Think all of the TAF sites will have a period of low
clouds tonight, though it should be early in the TAF period
at AUW/CWA, with low clouds departing RHI/GRB/ATW/MTW early
Friday morning.

Models continue to show fog/low stratus developing over the Fox
Valley and possibly NC WI overnight. Have added some MVFR/IFR fog,
especially at ATW and RHI, but confidence is low.

An arctic cold front will move through the forecast area Friday
afternoon. Light snow is expected to develop in association with
the front. Have used TEMPO groups to frame out the most likely 2-3
hour period of snow at each TAF site. Flight conditions will drop
to MVFR/IFR, with the lowest vsbys expected at the western TAF
sites. Even after the snow tapers off, MVFR ceilings will persist
well into the evening at most locations.

After light and variable winds overnight into early Friday, SW
winds will gradually increase before shifting W and gusting to
around 25 kts after the frontal passage in the afternoon/early
evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION.....MPC
AVIATION.......Kieckbusch