Winter Storm Warning 5, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
1125 PM CST Tue Dec 3 2024

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Periods of light snow/snow showers expected through Wednesday
  night with the highest risk of accumulations (50-90% chance of
  at least 2") across far northern Wisconsin. Brief visibility
  reductions will be possible in snow showers region-wide on
  Wednesday.

- Gusty west to northwest winds developing Wednesday into
  Wednesday evening (30 to 60% chance for gusts of at least 40
  mph) with colder air resulting in wind chills as low as 5 below
  to 10 below zero by Thursday morning.

- Temperatures will gradually warm heading into the weekend with occasional
  light snow/flurry chances, but any impacts look low at this
  time late this week and this weekend.

&&

.DISCUSSION...
Issued at 247 PM CST Tue Dec 3 2024

Tonight-Thursday: Turning colder, windy with areas of snow showers

Upstream surface obs and radar imagery shows an area of light snow
working across northern Minnesota and northwest Wisconsin this
afternoon, although dry low-level air will take some time to
saturate. This area of snow will translate east this evening with
the strongest synoptic lift/warm advection skirting by mainly across
far northern WI into the Upper Peninsula of Michigan. Overall,
amounts should be light with up to around an inch possible along the
WI/MI border.

On Wednesday, a strong mid-level trough will drive southeast across
the Great Lakes with a surge of strong low-level cold advection.
With steepening low-level lapse rates beneath the trough, expect
scattered snow showers to develop. Accumulations overall look
minimal with these, but brief visibility reductions could occur and
possibly result in a few slick spots. In addition, the cold
advection/steep lapse rates, combined with around 40 kts winds at
the top of the mixed layer will lead to strong, gusty northwest
winds. Chances for at least 40 mph winds from the 03.12Z HREF are
around 30 to 60 percent during the later afternoon/night on
Wednesday.

The strong push of cold air will result in falling temps Wednesday
afternoon. The gusty northwest winds and temps in the single digits
and teens will likely result in wind chills around 10 below zero in
spots on Thursday morning, so those heading outdoors Wednesday night
and Thursday will want to prepare for cold weather.

Some lake contribution to the snow will likely occur across north-
central WI Wednesday afternoon into Thursday, especially as winds
shift more northwesterly and the mixed layer deepens. Several inches
of snow are possible across Vilas County. Have coordinated with WFOs
Duluth/Marquette to hoist a Winter Weather Advisory for Vilas County
Wednesday/Wednesday evening. Overall, chances for at least 2" of
snow are confined mainly to north-central Wisconsin and Door County,
but highest across Vilas County.

Friday-Tuesday: Warming into the weekend, higher precip potential
early next week.

Heading through late week into early next week, northwest flow aloft
will relax with the mid-level flow shifting southwesterly by
Monday/Tuesday. After continued chilly conditions through Friday as
the Canadian surface high passes south and east, warmer air will
spread back across the area over the weekend, including highs
possibly eclipsing 40 degrees by Sunday. Overall, weather impacts
look low through the weekend with global ensembles (GEFS/EPS/CMC)
showing only low probabilities (10-30%) at times for light
snow/flurries associated with any weak waves in northwest flow.

Confidence in pattern evolution lowers early next week with a broad
trough forecast to evolve across the Rockies. There is considerable
spread in how this trough and smaller scale troughs progress during
this time, but an precipitation chances trend upward (30-50%) by
Monday of next week.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1125 PM CST Tue Dec 3 2024

Conditions varied between MVFR/IFR across northern Wisconsin in
snow showers, with MVFR/VFR conditions across central and
east-central Wisconsin with light snow at times. This area of snow
across the north will move out of the region during the overnight
hours, leaving MVFR conditions in place. Further south conditions
will continue to bounce between MVFR/VFR. Gusty southwest winds
will continue during the overnight hours.

A cold front will turn winds from west to northwest on Wednesday
morning. Scattered snow showers will also track through the region
with the cold front, reducing CIGs to MVFR.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 9 AM Wednesday to 6 AM CST Thursday
for WIZ005.
&&

DISCUSSION.....JM
AVIATION.......Kurimski

Hazardous Weather Outlook
National Weather Service Green Bay WI
245 PM CST Tue Dec 3 2024

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-042045-
Vilas-Oneida-Forest-Florence-Northern Marinette County-Lincoln-
Langlade-Menominee-Northern Oconto County-Door-Marathon-Shawano-
Wood-Portage-Waupaca-Outagamie-Brown-Kewaunee-Waushara-Winnebago-
Calumet-Manitowoc-Southern Marinette County-
Southern Oconto County-
245 PM CST Tue Dec 3 2024

This Hazardous Weather Outlook is for north-central and northeast
Wisconsin.

.DAY ONE...Tonight

Slick travel may develop tonight across northern Wisconsin,
generally north of a Wausau to Green Bay line from light snow
accumulations.

.DAYS TWO THROUGH SEVEN...Wednesday through Tuesday

Snow showers combined with winds gusting 30 to 40 mph will likely
result in slick to hazardous travel across northern Wisconsin
Wednesday into Wednesday night with brief snow showers and
visibility reductions possible elsewhere.

Wind chills will fall to zero to 10 below zero early Thursday.

.SPOTTER INFORMATION STATEMENT...

Any snowfall reports would be appreciated tonight through
Wednesday night.

LMZ521-522-541>543-042045-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
245 PM CST Tue Dec 3 2024

This Hazardous Weather Outlook is for portions of northwest Lake
Michigan and the waters of Green Bay.

.DAY ONE...Tonight

Conditions hazardous to small craft are expected this evening
into Wednesday morning.

.DAYS TWO THROUGH SEVEN...Wednesday through Tuesday

Northwest gales are likely late Wednesday afternoon into
Thursday.

JM

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