306
FXUS63 KGRB 311115
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
515 AM CST Wed Dec 31 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- An arctic front will bring light snow and flurries to the region
  today. Accumulations will generally be a dusting to a half inch,
  though 1 to 2 inches are possible across the snow belt of Vilas
  County due to lake effect.

- Bitterly cold air following the front will cause wind chills to
  drop between 15 below and 25 below zero late tonight through the
  morning of New Years Day.

- Intermittent chances for light, fluffy snow through the weekend
  as fast-moving clipper systems traverse the region.

&&

.DISCUSSION...
Issued at 252 AM CST Wed Dec 31 2025

The latest RAP analysis and satellite imagery show a potent
shortwave trough over far northwest Ontario driving an arctic
front south across Lake Superior and northern Minnesota early this
morning. A surface trough is currently positioned over the
central U.P. into far northern Wisconsin, while an area of reduced
visibilities indicative of light freezing drizzle is moving
through north-central Wisconsin. This front is poised to drop
south across the northern Great Lakes today, ushering in a
significantly colder airmass. Meanwhile, broad mid and upper-level
troughing is established across the eastern U.S. with a ridge
over the western states, creating a steady northwest flow regime
that will dominate the local weather pattern for the next week.

As the arctic front drops south across the area this morning,
light snow and flurries will increase along and behind the
boundary. The highest chances for accumulation will be centered
over Vilas County, where lake effect contributions from Lake
Superior will enhance totals. Expect 1 to 2 inches of accumulation
over the northwest half of the county, with only a dusting to a
half inch likely elsewhere. Impacts to travel should be minimal,
and most of the synoptic snow is expected to end by early evening
as the front clears the region.

The primary concern for New Years Eve and New Years Day will be
the arrival of a bitterly cold arctic airmass. While the pressure
gradient will remain strong enough to prevent winds from fully
decoupling, the combination of temperatures falling below zero and
a persistent 5 to 10 mph wind will result in bitterly cold wind
chills tonight into New Years Day. Wind chills are forecast to
fall to around 20 below zero across central and north-central
Wisconsin and near 15 below over the Fox Valley late tonight.
While these values are shy of cold weather advisory criteria by
around 5 degrees, they will still represent a hazard for those
outdoors tonight.

Beyond Thursday morning, the upper level pattern remains
relatively stable with fast-moving clipper energy generating
periodic light snow. Another weak round of frontogenesis may bring
a dusting to central Wisconsin on Thursday afternoon and evening.
This stable northwest flow will support additional clippers late
Friday night into Saturday, again on Sunday, and during the Monday
night through Tuesday timeframe. Each of these systems carries a
30 to 50 percent chance of producing a half inch or more of light,
fluffy snow. Temperatures will remain below normal through the
weekend before beginning to moderate toward the middle of next
week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 514 AM CST Wed Dec 31 2025

Early this morning, an arctic front was positioned across the
Upper Peninsula. A mix of IFR and MVFR conditions prevail across
north-central WI while a mix of VFR and MVFR ceilings prevail
across northeast WI. Lower visibilities to MVFR in mist or
freezing drizzle exist from about KAIG to the U.P. border.

As the arctic front drops south, snow may move back into RHI
around daybreak. The front will bring another round of light snow
and flurries (vsby mostly VFR, but as low as MVFR portions of
central WI) from about mid morning through mid afternoon, before
tapering off by late afternoon as the front shifts south. IFR
ceilings to linger thru 14-15z across north-central WI. But for
most, ceilings today will be mainly MVFR. Skies clear out this evening,
except over north- central WI where lake effect clouds and a few
flurries will linger.

Northwest winds will increase to 10 to 20 knots (gusts to 25 kts) as
the Arctic front moves through. Winds will diminish this evening.
Marginal wind shear conditions (medium confidence) will then
setup at RHI after about 03z Thu.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion