NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 210544
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1144 PM CST Tue Jan 20 2026

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Two weak clipper systems will bring periods of light snow to the
  region tonight through Wednesday evening. While total snowfall
  amounts will be minor, generally a dusting to one inch, some
  slippery stretches are possible on area roads for the Wednesday
  morning and afternoon commutes.

- A period of dangerous cold is expected Thursday night through
  Sunday morning. Wind chills are forecast to reach 30 to 45
  degrees below zero across much of north-central and northeast
  Wisconsin Friday morning and Saturday morning.

- An Extreme Cold Watch has been issued from midnight Thursday
  night through noon Saturday. This represents a dangerous
  situation for those outdoors without proper clothing.

&&

.DISCUSSION...
Issued at 220 PM CST Tue Jan 20 2026

The latest RAP analysis and satellite imagery show high pressure
centered over the southern Mississippi Valley and a weak surface
low over the central Great Plains. A large Hudson Bay upper low
continues to dominate the large-scale pattern across North
America, resulting in broad troughing over the Great Lakes and a
prominent ridge along the West Coast. In Wisconsin, arctic air
remains entrenched with current wind chills ranging from 10 below
to 20 below zero. Clouds are beginning to increase from the west
ahead of an approaching clipper system currently tracking across
Montana. This system, followed by a second clipper on Wednesday,
will be the primary weather drivers for the next 36 hours before
a more significant arctic surge arrives Thursday night.

Light Snow through Wednesday: The near term focus remains on two
weak clipper systems traversing the region. The first upstream
clipper will track into the southern Great Lakes tonight. Clouds
will thicken and lower this evening, with deep saturation first
being achieved over central Wisconsin late this evening before
spreading northeast overnight. A dusting to a half inch of snow is
possible south of a line from Marshfield to Kewaunee, with
flurries and a thin dusting elsewhere. A second clipper will drop
south from the Canadian arctic Wednesday afternoon, bringing
another period of light snow after 2 pm. While total accumulations
from both systems will be light, the timing could impact the
Wednesday commutes with slippery stretches on area roads.
Temperatures on Wednesday will provide a brief reprieve from the
deep freeze, with highs reaching the middle teens to lower 20s.

Extreme Cold Thursday night into the Weekend: The main focus of
the forecast is the arrival of dangerous arctic air late this
week. While a brief period of moderation is expected Wednesday, a
powerful arctic front will sweep through the region Thursday
evening. This front is associated with the southward movement of
the polar vortex from northern Minnesota into northern Wisconsin.
850mb temperatures are progged to plummet to between 30 and 35
degrees below zero by late Thursday night. Surface temperatures
will fall into the 10 below to 25 below range, and when combined
with sustained winds of 10 to 20 mph, wind chills are likely to
reach 30 to 45 below zero by early Friday morning.

Below zero highs are likely on Friday. High temperatures have
trended slightly colder, but afternoon wind chills will only
moderate into the 20 below to 35 below range. Some guidance
remains colder than this, and there is some room for temps to
trend even colder in coming forecast cycles.

High pressure will settle over the region Friday night, which may
lead to the coldest actual air temperatures of the season if
winds decouple. Given high confidence in these life- threatening
conditions, an extreme cold watch has been issued for the entire
area from midnight Thursday night through Saturday morning.

Slow moderation looks to occur late in the weekend into early next
week, but temps to remain below normal into next Tuesday. As
temperatures moderate, low predictability exists for snow chances.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1144 PM CST Tue Jan 20 2026

Very light snow began to fall in portions of central WI late this
evening on the northern periphery of a clipper system. This
clipper system will bring MVFR cigs/vsbys and light snow to
portions of central and east-central WI into early Wednesday
morning. Confidence remains highest at the MTW TAF site to see
MVFR cigs/vsbys from this clipper system, while confidence has
lowered elsewhere.

By early Wednesday morning, forecast soundings indicate low-level
moisture will increase across central and north-central WI,
resulting in MVFR or IFR cigs and potential light snow or
flurries. Meanwhile, the east-central WI TAF sites will remain
with VFR conditions.

Another round of light snow is progged to move southeast across
the region Wednesday afternoon. This will keep the MVFR/IFR cigs
at the central and north-central WI TAF sites and reduced vsbys
through Wednesday evening, with MVFR cigs/vsbys arriving at the
east-central WI TAF sites for the afternoon through the evening.

Southwesterly winds will remain light through most of this TAF
period, but increase Wednesday afternoon and again in the evening
from the west with gusts of 15 to 20 kts. There also appears to
be a brief period of LLWS Wednesday evening as winds above the
surface will be from the northwest around 40 kts.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Extreme Cold Watch from late Thursday night through Saturday
morning for WIZ005-010>013-018>022-030-031-035>040-045-048>050-
073-074.
&&

$$

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