NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 201705
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1105 AM CST Tue Jan 20 2026

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Bitter cold wind chills of 20 to 30 below zero are being
  observed across the region early this morning. Cold Weather
  Advisories are in effect until 10 am today.

- Light accumulation of snow is expected for locations along and
  south of a Sturgeon Bay to Stevens Point line late this evening
  through Wednesday morning. 40-70% chance for at least one tenth
  of an inch.

- Another wave of bitter cold Thursday night through this
  weekend, with wind chills of 30 below zero or colder possible
  Friday morning and Saturday morning.

&&

.DISCUSSION...
Issued at 306 AM CST Tue Jan 20 2026

Bitter Cold This Morning...

As of 3AM this morning wind chills ranged generally from -20 to -35
degrees across the region. As winds back around to the southwest
today air temps will warm into the middle single digits to low teens
with wind chills in the single digits above and below zero. Cold
Weather Advisory is still slated to end at 10AM this morning,
however, exactly when temperatures rise above criteria may range
from about 9AM to Noon today.

Light Snow Tonight into Wednesday...

Latest run of CAMs (20.00Z) continues to trend the strongest forcing
further south with a clipper system progged to swing across the
region tonight into Wednesday morning. This has resulting in the
higher QPF and snowfall amounts being shunted across southern WI.
However, even with just a few hundredths of QPF now expected south
of HWY 29 snowfall should be very efficient as the entire saturated
column resides in the DGZ creating SLR of 19/20:1. NBM probs show a
20-30% chance for greater than 1" along and south of HWY 10. South
of a line from Sturgeon Bay to Stevens Point there is a 30-70% for
at least one tenth of an inch of snow. In terms of timing with this
system onset of snow in central WI is expected around or just after
midnight and will spread east through the early hours of Wednesday
morning. This will be a quick hitting system as much of the snow
will be pushing off to the east by 9-10AM. There will likely be some
minor impacts to the Wednesday morning commute, mainly around the
Fox Valley due to snowcovered and slippery roads. Holding off on any
Winter Weather headlines at this point, however, depending on trends
would not rule out a Winter Weather Advisory being needed for our
souther row of counties.

A secondary shot-wave may also bring a dusting of snow late
Wednesday afternoon/evening to parts of central WI. However,
uncertainty is higher during this period drier mid-level air will be
filtering into the region.

Extreme Cold Thursday night into the Weekend...

Another arctic high pressure system is progged to deliver bitterly
cold temperatures back to the region Thursday through Saturday. 850mb
temps at the core of the system are forecast to reach -35C which is
in the 1st percentile of climatology. Air temperatures Thursday night
into Friday are forecast to range from -10F to -25F and with a
steady 10-15 mph northwest breeze wind chills will approach -30F to -
40F across most of the region. Even colder air temperatures are
expected Friday night into Saturday with lows ranging from -15F to -
30F. However, with calm winds wind chills won't be quite as cold as
the previous night. Confidence is high with these dangerously cold
temperatures to end the week, there is a 100% chance Cold Weather
headlines will be needed, question will be what areas reach Extreme
Cold Warning criteria (-30F apparent temperatures for east-central
and northeast WI and -35F apparent temperatures for central and
north-central WI).

Expect Sunday will mark the end of this cold snap as temperatures
beginning to trend slightly warmer each day through the first half of
next week.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1105 AM CST Tue Jan 20 2026

VFR conditions will prevail through early this evening across all
terminals with gusty west to southwest winds of 15-20 kts. Low-level
moisture will increase tonight as a clipper system moves into the
region. Expect a transition to MVFR (or low end VFR at the very
least) ceilings after 04z-07z as cloud bases lower and light snow
develops across parts of the area.

Confidence is lower than normal regarding the intensity and coverage
of snow overnight through Friday morning. Confidence is highest
for reduced visibilities in light snow at MTW. However, forecast
soundings indicate ample low level moisture that could lead to
flurries across much of the region that could temporarily reduce
visibilities below VFR. Potential snow accumulations of a dusting
to a half inch look possible. Some improvement of ceilings to VFR
is expected on Wednesday morning.

Winds aloft look a bit too marginal for low level wind shear in
the forecast.

&&

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

&&

$$

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