063
FXUS63 KGRB 071742
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1142 AM CST Sun Dec 7 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- A clipper system is expected to bring a swath of 1 to 3 inches
  of snow to the northeast two-thirds of the forecast area area
  Monday night into early Tuesday morning. Locally higher snowfall
  amounts are possible across Door County where snowfall totals
  may be enhanced due to lake effect snow showers off Lake
  Michigan.

- A more potent clipper system is expected to bring another round
  of snow to the area Tuesday afternoon into Wednesday morning.
  This system could produce a band of snow of 3-6 inches with
  locally higher amounts. There is still some uncertainty in where
  the axis of heaviest snow will set up across the area.

- Temperatures will moderate some by the middle of the week, then
  turn colder again Thursday into next weekend. There is a fairly
  large spread in the guidance temperatures during this period,
  but based on 850mb temperatures would suggest the colder
  guidance will be more likely to occur.

&&

.DISCUSSION...
Issued at 222 AM CST Sun Dec 7 2025

Short Term...Today...Tonight...and Monday

An area of light snow across central and east-central Wisconsin
will come to an end from west to east this morning as dry air
advects into the region. Dry weather is then expected for the rest
of the morning and into the afternoon as well as tonight as high
pressure tracks through the western Great Lakes region. Cold air
will filter in behind the departing snow, with temperatures
expected to fall throughout the morning, then rise a bit through
early afternoon, and fall again by mid to late afternoon. A period
of clear skies this evening will allow temperatures to plummet
below zero west of the Fox Valley, with temperatures in the single
digits above zero east of the Fox Valley towards the lakeshore.
Clouds advecting in from the west will keep temperatures from
falling further overnight.

Winds will turn southerly Monday on the backside of the departing
high pressure system, which will allow temperatures to recover a
bit into the upper teens across the north with lower 20s across
east-central Wisconsin. The southerly winds will bring the chance
(20-30%) for some light lake effect snow across the lakeshore
counties despite warm air advection as delta T values will be in
the middle teens. Snowfall amounts across the lakeshore
should be fairly limited as the main lake effect bands currently
do not look to make it onshore, with a dusting of accumulation
possible. Further west, the warm air advection will bring
a small chance (10-20%) for flurries or light snow to the rest of
the region Monday afternoon.

Long Term...Monday Night Through Saturday

No real changes in the 500mb pattern through the period as
a few clipper systems move across the region. For Monday
night into Tuesday morning, the first clipper system will bring
a swath of snow to the area. Snowfall amounts of 1 to 3 inches
are expected north of Wausau to Green Bay to Manitowoc line. Will
need to watch the lakeshore, as some lake effect snow showers may
move onshore off Lake Michigan to enhance snowfall totals,
especially across Door County. The NBM probabilities for
greater than >3 inches of snow was only 5-25% across the north,
except over northern Door County where the chance was up to near
35%.

After a brief break in the actions, a more potent clipper system
will spread snow into the area Tuesday afternoon, with snow
continuing Tuesday night before tapering or ending later Tuesday
night or Wednesday morning. Models consistent in showing a
heavier band of snow ranging from 3-6 inches is likely across
portions of the area. Locally higher amounts are also possible.
The main question is where the highest snowfall totals will end
up. The ECMWF has trended slightly northward from the its run
last night, which was supported by the NAM. The Canadian was
slightly south, although was consistent with the run last night.
The GFS solution was a split of the ECMWF/Canadian solution.
Either way, this system will bring an impactful snowfall for
travelers by car or air. The probabilities of 3 inches or more
of snow is 60-80% in the axis of heavier snowfall. Will continue
to monitor over the next few days as there may be some variations
in the different solutions from model run to run, and amongst
the different models.

The confidence in the chances of light snow at the end of the
week is low. Clipper system is still expected to pass to the south
of the area Thursday. After a moderation in temperatures Tuesday
and Wednesday. colder air works in the region Thursday into next
weekend. Looking at the box and whisker plot at Green Bay, a
pretty large range in the max/min temperatures Thursday into next
weekend. Looking at the model 850mb temperatures, thinking the
colder guidance is more likely to occur. Would not be surprised if
temperatures trend lower on some days with future forecasts.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1134 AM CST Sun Dec 7 2025

Lake-enhanced low clouds (MVFR) covered north central and parts of
far northeast WI at issuance time, but any southward advancement
had ended. Will carry MVFR ceilings at RHI until around 21z, with
the expectation of clearing after that time. High/mid clouds will
increase overnight, and models strongly hint at some low cloud
(MVFR) development as south winds and associated WAA strengthen
late Monday morning. The forecast still looks on track for
accumulating snow Monday night, with the most significant amounts
(1-3 inches) occurring over the northeast half of the forecast
area.

&&

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

&&

$$

DISCUSSION.....Kurimski/Eckberg
AVIATION.......Kieckbusch