NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 210451
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1051 PM CST Sat Dec 20 2025

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Colder air moves in tonight with wind chills falling to 10 to 20
  below in spots overnight, lowest over central and north-central
  Wisconsin.

- Although no significant weather systems are on tap heading
  into the start of the holiday week, there are medium (40-70%)
  chances for at least an inch of snow over parts of northeast
  Wisconsin Sunday night and Monday, and smaller chances (<20%)
  for a light wintry mix/freezing drizzle during this time.

- Beyond Sunday, above average to well above average
  temperatures will prevail through the week.

&&

.DISCUSSION...
Issued at 208 PM CST Sat Dec 20 2025

Tonight-Sunday: Gusty winds this afternoon, turning colder

A cold front is pushing southeast across the area this afternoon
with a surge of strong low-level cold advection in its wake.
Deepening mixing and winds near 45 kts at the top of the mixed layer
with fairly unidirectional westerly flow will lead to a period of
gusty winds into the evening, up to 40-45 mph in spots at times.
This will lead to some drifting/patchy blowing snow and locally
slick travel, especially across northern Wisconsin where a
fresh coating of snow fell last night. Wind chills will fall
below zero in most locations overnight and early Sunday with 10
to 30 percent chances for wind chills dropping to 20 below for a
time early Sunday morning across central Wisconsin.

Winds will be much lighter on Sunday as high pressure passes across
the region, but temperatures will remain below average for Sunday.

Sunday night-Monday: Light snow/wintry mix

A quick-moving shortwave trough will slide through Sunday night into
Monday as the flow becomes more zonal aloft and warmer air starts to
return northward. A swath of warm advection/frontogentically induced
precip will spread east with the wave, although there is some
lingering uncertainty in placement, degree of dry air, and thermal
profiles. Overall, precip amounts look modest, and the highest
chances for at least an inch of snow (40-70%) are centered across
northeast Wisconsin. Depending on the degree of saturation and mid-
level warming, some mixed precip cannot be ruled out. ECMWF ensemble
precip types do show a low (<10-20%) for light freezing rain/drizzle
on Monday/Monday evening, especially from central into east-central
Wisconsin. This will not be a major system, but there could be some
minor impacts to travel.

Tuesday-Saturday: Warmer, low precip chances

Global ensembles are in strong agreement for mid-level ridging to
overspread the central US for much of Christmas week, resulting in
high confidence for above average temps. Mean 850 mb
EPS/GEFS/Canadian ensemble temps towards Christmas Day are near the
top of climo and there are medium (40-70%) chances for highs of at
least 40F by Christmas Day.

Although there is little signal for any significant weather systems
to impact the area through late week, a few embedded shortwave
troughs in the west to southwest flow may bring some light
precipitation at times for mid to late week, including one system on
Wednesday, but precip chances are low at this time (<30%). With
southerly flow over cold ground and stronger moisture return by mid
week (precipitable water values exceeding the 90th percentile), will
have to watch for low stratus/fog development. Probabilities for
above freezing dew points increase Wednesday and Christmas Day
(above 80% for many areas), often a favorable signal for widespread
fog/stratus.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1050 PM CST Sat Dec 20 2025

Winds will steadily diminish through the overnight. Winds on Sunday
will be light. LLWS is possible Sunday night central to north-central
WI ahead of next plains system.

Conditions will be VFR through the TAF period. Snow will spread
across the region late Sunday night.

&&

.MARINE...
Issued at 208 PM CST Sat Dec 20 2025

Post frontal westerly flow and deepening mixing will promote a
period of gale force gusts this afternoon and evening. As high
pressure begins to approach on Sunday morning, winds will slowly
subside. Issued a Small Craft Advisory for the overnight hours as
winds remain gusty, but drop below gale force. Small Craft Advisory
conditions may develop again on Monday as southerly winds and waves
increase.

&&

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

&&

$$

DISCUSSION.....JM
AVIATION.......JLA
MARINE.........JM