139
FXUS63 KGRB 281659
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1059 AM CST Fri Nov 28 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- A winter storm will impact the region Saturday and Saturday
  night. Heavy snow is expected across central and east-central
  Wisconsin, where 6 to 9 inches of accumulation is forecast.
  Locally higher amounts exceeding 10 inches are possible near
  Lake Michigan.

- A Winter Storm Warning has been issued from Wood County to Door
  County. A Winter Storm Watch is in effect for Marathon, Shawano,
  Menominee, Oconto, and Southern Marinette counties where there
  is greater uncertainty in snowfall totals.

- Much colder air will arrive for the start of next week. Wind
  chills may fall to 10 below zero or colder Monday morning.

&&

.DISCUSSION...
Issued at 348 AM CST Fri Nov 28 2025

The latest RAP analysis shows a deep upper cyclone spinning over Quebec to the
eastern Great Lakes this morning, keeping the Great Lakes region in cyclonic
flow. To the west, high pressure stretches north to south across the Great
Plains. Between these features, a thermal troughing regime resides over
Wisconsin. Upstream, a potent shortwave trough is moving across the Pacific
Northwest while a lead shortwave traverses Montana. As energy from the Pacific
Northwest moves into the center of the country and triggers surface
cyclogenesis, impacts from a strong winter system remain the focus of this
forecast.

Short Term (Today through Saturday Night):

Relatively quiet weather is in store for today as weak high pressure builds
into the region. Light lake effect snow showers will continue over the
snowbelt of north-central WI, but these are on track to end this afternoon
with less than an inch of additional accumulation. Attention then turns to
the approaching winter storm. Clouds will rapidly return and lower tonight
into early Saturday morning ahead of the system. While light snow may spread
across the northern Mississippi Valley late tonight in a warm advection
pattern, dry air associated with the arctic high is expected to hold off
precipitation in our area until Saturday morning. Increasing isentropic
ascent and the arrival of the right rear quadrant of a jet streak will provide
the necessary forcing for precipitation to overspread the region on Saturday
morning.

Forcing and moisture parameters will intensify Saturday afternoon and evening.
The track of the surface low has shifted slightly further north in recent
guidance, placing a greater portion of the forecast area into the potential
for heavy snow. Consequently, QPF and snow amount forecasts have increased.
The heaviest snow is expected to track across east-central WI from late
Saturday afternoon through Saturday evening, where probabilities of 1 inch
per hour snowfall rates reach upwards of 40%. This intensity is due in part
to lake enhancement and the presence of an inverted trough along the western
shoreline of Lake Michigan. Lake-induced instability parameters are impressive,
with delta-Ts upwards of 16-17C. Forecast soundings also depict a deep
dendritic snow growth zone of 150-200mb depth, which should lead to efficient
snowfall production.

Probabilities for greater than 6 inches of snow now exceed 80% from Wood
County to Door County. Given this high confidence, a busy travel
weekend, and coordination with surrounding offices, a Winter
Storm Warning has been issued for this corridor. A Winter Storm
Watch has been maintained on the northern flank of the warning
(Marathon, Shawano, Menominee, Oconto, and southern Marinette
counties) where uncertainty regarding in QPF remains higher. The
heaviest snow will depart after midnight Saturday night. Current
forecast totals range from 1 to 2 inches over Vilas County to 6 to
9 inches over east-central WI, with locally higher amounts in
excess of 10 inches possible near Lake Michigan in Kewaunee and
Manitowoc counties.

Long Term (Sunday through next Thursday):

Low pressure will exit the eastern Great Lakes into Quebec on Sunday. Light
snow will diminish across the region Sunday morning, with up to a half inch
of additional accumulation possible. Scattered light lake effect snow showers
will likely linger over far north-central WI until Sunday night. By this
point, arctic air will be firmly entrenched, with high pressure dominating
the pattern through Monday. Chilly temperatures are in store for this period,
with lows expected to drop below zero across the Northwoods Sunday night.
Wind chills are forecast to range from 0 to 10 below zero region-wide, except
near Lake Michigan.

We will be monitoring a system passing to the south of the area on Monday and
Monday night. While this system has trended slightly north in some models,
prompting the addition of low chances for light snow Monday night, the
majority of guidance keeps precipitation south of the area. Therefore,
confidence remains low that snow will impact the region early
next week. An arctic front will approach the area by midweek,
bringing the next chance of snow next Wednesday.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1053 AM CST Fri Nov 28 2025

Scattered light snow showers or flurries north and west of the
Fox Valley will come to an end this afternoon, by 22z. Attention
then turns to a winter storm that will impact the area, beginning
between 14z and 18z Saturday for much of the area and continue
into Sunday morning, probability of snow from 85-100%. The
heaviest snow will fall Saturday afternoon and Saturday night.
Behind the system, gusty northerly winds are expected late
Saturday night and Sunday, with gusts of 25-30 kts that could
produce some blowing and drifting of the snow.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Saturday morning through late Saturday
night for WIZ020-021-030-031-073-074.

Winter Storm Warning from 9 AM Saturday to 6 AM CST Sunday for
WIZ022-035>040-045-048>050.
&&

$$

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