317 
FXUS63 KGRB 061750
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1150 AM CST Sat Dec 6 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- For tonight into Sunday morning, there is a 30-50% chance for
  greater than 1" of snow south of a Marshfield to Sturgeon Bay 
  line. Elsewhere accumulations around an inch or less are 
  expected. Chances of light snow taper off over northern WI. 

- A clipper system is expected to bring a round of snow (60-90%)
  Monday afternoon into early Tuesday morning, bringing a few
  inches of snow. The highest totals are expected across the 
  north and far northeastern WI. 

- A more potent clipper system is expected to bring another round
  of snow (70-90%) to the area Tuesday night and Wednesday. There
  are indications that a band of 3-6+ inches of snow is possible 
  with this system, although there is a lot of uncertainty in 
  where this heavier band of snow will set up. 

- Below normal temperatures will continue through the weekend with
  moderating temperatures by the middle of next week. Temperatures
  across central and east-central WI could flirt with the freezing
  mark Tuesday or Wednesday.

&&

.DISCUSSION...
Issued at 221 AM CST Sat Dec 6 2025

Short Term...Today...Tonight...and Sunday

Other than lake effect snow across far north-central Wisconsin
through this morning, dry weather is expected across the region
today as a weak ridge of high pressure tracks through the western
Great Lakes region.

A low pressure system tracking through the mid Mississippi Valley
will bring the next chance for snow to the region tonight into
early Sunday morning. While the best forcing and moisture are
expected to be across southern Wisconsin, there will be enough
frontogenesis and moisture across central and east-central
Wisconsin to bring a few inches of accumulating snow. Current NBM
probabilities for exceeding 1" of snow have risen slightly to 30
to 50% south of a line from Marshfield to Sturgeon Bay with 
10-20% probabilities for exceeding 2" across roughly this same 
area. Therefore, snowfall amounts across central and east- central
Wisconsin are expected to come out to be around 1 to 2 inches.
Further north dry air will keep snow totals under an inch with
only light snow or flurries expected. Dry air pushing in from the
northwest should bring a rather quick end to the snow Sunday 
morning with most of the region turning dry by the afternoon.

Long Term...Sunday Night Through Friday

500mb pattern defined by ridging across the western U.S. with 
downstream troughing over the eastern U.S. The active northwest 
flow pattern will result in several clipper systems moving across 
the region during the forecast period, along with temperatures
running below normal on most days. 

For Sunday night, high pressure will slide east across the area.
With winds diminishing, the question is how far temperatures 
drop Sunday evening into the early hours on Monday before clouds
arrive which will result in temperatures rising late. Did lower
min temperatures by a few degrees, especially in our typically
cold spots over central and north-central WI. On Monday, our
attention turns to the lakeshore where light low level winds 
turn onshore during the morning. Lake to 850mb temperatures
differences of 13-15C may result in some snow shower or flurry
activity near Lake Michigan. Door County would be the most likely
candidate for some accumulating snow on Monday off the lake before
the main system arrives from the northwest later Monday afternoon
and evening. 

On Monday night and Tuesday, clipper system will bring snow to
the area, with chances of snow at 60-90%. Probabilities of 1" of
snow is 50-80% north of a Wausau to Green Bay to Kewaunee line
while the probability of 3 inches is only 20-40% along the Upper
Michigan border. With the track of the clipper system, some milder
air will work into the area with high temperatures reaching the
lower 30s. across central and east-central WI. Meanwhile, a more 
potent clipper system is expected to bring another round of snow 
(70-90%) to the area Tuesday night and Wednesday. There are 
indications that a band of 3-6+ inches of snow is possible with 
this system, although there is a lot of uncertainty in where this 
heavier band of snow will set up. Confidence is growing for an 
impactful event across the western Great Lakes based on the
NBM probabilities this far out with 40-70% chance of 3 inches 
and 30-50% chance for 6 inches. Being five days out, the question 
is where this band of heavier snow will set up. The latest 
model run of the ECMWF/Canadian model has shifted this band a 
little further south compared to last night while the GFS was
a tad bit further north with the axis of heavier snow. I suspect 
the models will continue to shift from run to run on where this 
axis will setup. Will wait and see! Otherwise, potentially another
clipper system Thursday and Thursday night, but latest ECMWF and 
Canadian are trending southward with this system, thus impacts are
uncertain at this time. Colder air will work back into the region
later in the week, although some differences noted in the colder 
GFS and warmer ECMWF guidance Friday into next weekend.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1141 AM CST Sat Dec 6 2025

Observations showed a mix of VFR and patchy MVFR conditions at
issuance time, along with scattered flurries in spots. These
conditions should persist into the early evening. A low pressure
system passing well south of the region will bring some light snow 
to central and east central WI later this evening and into the
overnight hours, with vsbys dropping into the MVFR/IFR categories.
An inch or two of accumulation is possible in the far south part 
of the forecast area, so some plowing operations may be needed
there. The snow will end by daybreak Sunday, followed by a quick
return to VFR. The exception could be in north central WI, where
NNW winds may generate lake-enhanced clouds and MVFR ceilings 
later tonight into Sunday morning.

&&

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

&&

$$

DISCUSSION.....Kurimski/Eckberg
AVIATION.......Kieckbusch