681
FXUS63 KGRB 021724
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1124 AM CST Fri Jan 2 2026

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Cold wind chills between 10 below and 15 below zero can be
  expected this morning, primarily over parts of central and
  north-central WI.

- Another clipper system will bring a dusting to a half inch of
  light snow to the area on Saturday.

- Confidence is increasing for a more potent clipper system to
  impact the region Sunday afternoon and Sunday night, bringing
  accumulating snow and a period of freezing drizzle into Monday
  morning. Probabilities of 3 inches or more of snow have
  increased into the 40-60% range along the U.P. border to
  northern Door County.

&&

.DISCUSSION...
Issued at 214 AM CST Fri Jan 2 2026

The latest RAP analysis and satellite/radar imagery show arctic
high pressure stretching from the northern Plains to the central
Mississippi Valley early this morning. Overcast conditions have
persisted into the early overnight hours, but clearing associated
with drier low-level air is making inroads south across northern
Minnesota and Wisconsin. This drier air should lead to clearing
over central to northeast Wisconsin later this morning, though
north-central Wisconsin should take longer to clear due to lake-
effect clouds. To the west, the next clipper system is already
observed on water vapor imagery over British Columbia and will be
the primary weather producer for the region on Saturday.

Arctic high pressure will remain the dominant feature across the
region today, maintaining the clearing trend through the morning
hours. While ample sunshine is expected for much of the day,
temperatures will remain quite cold with highs only reaching the
low to mid teens. The primary concern through this morning remains
the cold wind chills, which are currently ranging from 5 below to
15 below zero. These values will linger through the morning
before slowly moderating this afternoon as the core of the arctic
air begins to shift eastward.

Cloud cover will increase late today and tonight as moisture
ahead of the first clipper system begins to saturate the mid and
upper levels. As saturation becomes sufficiently deep, cloud bases
will lower, leading to a chance of light snow over central and
north-central Wisconsin very late tonight and expanding across the
rest of the region Saturday morning. While deep saturation could
persist into Saturday afternoon, snowfall amounts with this
initial wave look light, generally resulting in a dusting to a
half inch of fluffy snow. A gradual warming trend will commence on
Saturday, with high temperatures rising into the middle teens to
lower 20s.

A more substantial weather system is expected to track through
the western Great Lakes Sunday afternoon into Sunday night.
Dynamics with this clipper look much more impressive, featuring
potential for coupled jet streaks aloft and a 30-40 kt low-level
jet pointed at northern Wisconsin. Probabilities for a quarter
inch of liquid equivalent have trended higher, and there is now a
40-60 percent chance of snowfall amounts exceeding 3 inches across
far northern Wisconsin. Snow ratios will likely be below
climatology given a nearly isothermal layer around
6C and this constrains the higher end accumulations unless QPF
increases substantially. As mid- level moisture strips out at the
tail end of the system, a favorable window for freezing drizzle
will develop late Sunday night into Monday morning. This could
lead to a light glaze of ice on top of fresh snow, potentially
impacting the Monday morning commute and school traffic.

For the extended period, the latest ensemble means indicate a
slowly evolving pattern as the eastern U.S. trough lifts and an
upper ridge over the central U.S. slides east and becomes more
zonal. This shift will usher in a much warmer airmass for next
week, with high temperatures consistently in the low to middle
30s. The arrival of this warmer air will increase the complexity
of the precipitation types for future systems. Another system
could impact the region late Monday night into Tuesday, followed
by a potential system late in the week, both of which would likely
bring a mix of rain and snow. Confidence in the details of these
mid to late-week systems remains low due to significant
uncertainty in thermal profiles and precipitation placement.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1119 AM CST Fri Jan 2 2026

VFR conditions will give way to MVFR CIGS and VSBYs at most
places late tonight into Saturday morning as the next clipper
system will bring another round of light snow. Most locations
should see under an inch of snow. CIGS and VSBYs will gradually
improve Saturday afternoon as the steady light snow tapers off to
scattered snow showers or flurries before ending. A more potent
system will bring several inches of snow to northern Wisconsin
late Sunday afternoon and Sunday night. The snow could end as a
little freezing drizzle.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion