301
FXUS63 KGRB 011730
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1130 AM CST Thu Jan 1 2026

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Bitterly cold wind chills between 10 below and 20 below zero can
  be expected this morning and again late tonight.

- A fast moving clipper system is likely (60-80% chance) to bring
  a dusting to a half inch of snow today, especially across
  central and east-central Wisconsin.

- Intermittent chances for light, fluffy snow through the weekend
  and into early next week as fast-moving clipper systems traverse
  the region. There is a 50% chance of at least 1 inch of snow
  from far north-central Wisconsin to Door County on Sunday
  afternoon into Sunday night.

&&

.DISCUSSION...
Issued at 229 AM CST Thu Jan 1 2026

The latest RAP analysis and satellite/radar imagery show arctic
high pressure spreading southeast across the northern Mississippi
Valley and far western Great Lakes early this morning. Northwest
winds downstream of the surface high continue to produce scattered
to overcast conditions over north-central and far northeast
Wisconsin, with scattered flurries lingering from Vilas to Door
county. Despite the arctic airmass, the combination of cloud cover
and sustained winds of 5 to 10 knots has kept surface
temperatures just above zero in most spots. Wind chills are
approaching 15 below at some locations over central and north-
central WI. Looking to today, attention is focused on an Alberta
clipper currently located over southeast Saskatchewan and
southwest Manitoba, which will be the primary driver for our
weather over the next 24 hours.

The main focus for today revolves around the potential for light
snow accumulations associated with the aforementioned clipper
system. As low-level wind trajectories back to the west, lake
effect clouds and flurries should retreat toward the Michigan
border this morning. However, mid and high clouds will be on the
increase ahead of the approaching clipper. Given the dry arctic
airmass in place, it will take some time for the low levels to
saturate, but a brief window of deeper saturation is expected
across central and east-central Wisconsin from late morning
through mid-afternoon. While omega is centered relatively high in
the column between 700-500 mb, thermal profiles suggest high snow
ratios are possible. However, there is some uncertainty whether
these ratios will be realized as winds aloft may shatter
dendrites into smaller pieces. Still, increased moisture and
forcing should support around a half inch of fluffy accumulation
from central Wisconsin through the Fox Valley, which could create
some slippery travel conditions. Accumulating snow will depart by
late afternoon, though flurries could linger into the early
evening.

Bitterly cold conditions will remain a concern through the
morning. Wind chills are currently falling into the 10 below to
15 below range and are expected to bottom out between 15 below
and 20 below zero this morning.

Temperatures will not be quite as cold tonight. Winds will begin
to ease tonight as high pressure builds in, which may promote
decoupling and allow temperatures to plummet in typical cold
spots. Despite the lighter winds, wind chills will bottom out in
the 10 below to 20 below range tonight.

A gradual clearing trend is expected overnight, leading to a
sunny but cold Friday with high temperatures recovering into the
teens as high pressure takes control.

The long term pattern features a stable synoptic setup with broad
mid-level troughing over eastern North America and a ridge over
the Rockies. This configuration places an 850mb thermal gradient
over the western Great Lakes, with northwest flow aloft steering
several fast-moving clippers across the region. The first system
arrives on Saturday, potentially bringing light, fluffy snow to
the area, with the highest probabilities near the Michigan border.
A more potent clipper is progged to track across the region
Sunday afternoon and Sunday night. Accumulations with this system
have trended higher, with a 50 percent chance of greater than 1
inch of snow from the Michigan border to northern Door County.
Yet another system may target far northern Wisconsin Monday night
into Tuesday, though precipitation type may become an issue as the
core of the arctic air retreats into Canada. Temperatures will
remain below normal through the weekend before moderating to above
average levels by early next week.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1130 AM CST Thu Jan 1 2026

Other than MVFR ceilings over north-central WI, mainly VFR
conditions prevailed across the region late this morning. A
clipper system will continue moving through Wisconsin this
afternoon, which will cause clouds to thicken and lower to MVFR. Mid-
level dry air has delayed saturation, but a 3 to 4-hour window of
light snow is expected to impact most terminals through 21Z.

MVFR ceilings between 1500-2500 ft AGL are forecast to develop as
the snow arrives. Visibilities may briefly drop to 1-3 SM
(IFR/MVFR) within the steadiest snow. Snow accumulations around a
half inch are possible.

The accumulating snow will depart by 21Z, though flurries may
linger into the early evening. High pressure building in tonight
will lead to a clearing trend and lightening winds, with VFR
conditions returning to all sites after 04-06Z Friday.

Confidence is high regarding the occurrence of snow, but medium
on exact timing of the lowest visibilities.

Outlook...VFR on Friday. Additional light snow and MVFR potential
returns Saturday and Sunday.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion