397
FXUS63 KGRB 271152
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
552 AM CST Sat Dec 27 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Areas of freezing fog may create slippery conditions on
  untreated surfaces in north central and central WI this morning.

- Winter Storm Watches have been posted for the entire forecast
  area, for the potential for heavy snow and considerable blowing
  and drifting snow, from late Sunday afternoon through Monday.
  Treacherous travel conditions are likely, and some tree damage
  and power outages are possible.

- Strong northwest winds gusting to 35 to 50 mph inland, and gale
  or storm force gusts to 45 to 50 knots on Lake Michigan, are
  anticipated from late Sunday night through Monday evening.

- A surge of below normal temperatures is likely towards the New
  Year`s time frame. Wind chills as cold as 15 to 25 below zero
  are possible Thursday morning and Friday morning.

&&

.DISCUSSION...
Issued at 426 AM CST Sat Dec 27 2025

Changes with this forecast package: Have expanded the Winter
Storm Watch to the entire forecast area starting late Sunday and
continuing through Monday, for the potential for heavy snow or a
combination of snow and blowing and drifting snow. Have also
issued Gale/Storm Watches from late Sunday night through Monday
evening, with storm force gusts most likely near Deaths Door.

Areas of fog were forming over the northwest half of the forecast
area early this morning. Freezing fog and locally icy roads may
occur over parts of north central and central WI through the
morning hours. Elsewhere, widespread low stratus clouds covered
the region.

Despite developing southerly return flow today, a lack of deep
saturation will result in a dry day across most, if not all of the
forecast area. Highs should reach the middle to upper 30s.

Impacts of the incoming weekend system begin tonight, with pre-
frontal WAA leading to patchy light rain or drizzle. Low-level
thicknesses suggest all liquid precipitation, though spotty
freezing drizzle could occur in northern late tonight. Overall,
not expecting any significant impacts. That will change later
Sunday into Sunday night as a potent upper level low approaches
from the Northern Plains, inducing a rapidly deepening low
pressure system ("bomb" cyclone) that moves into the Lake Michigan
(interacting with the relatively warm waters) and Lower Michigan
areas Sunday night, then into southeast Ontario on Monday. Models
continue to trend higher with QPF/snowfall and winds, leading to
increased potential for heavy snowfall, strong winds, blowing and
drifting snow and possible gusts up to storm force on Lake
Michigan. Expecting a foot or more of snow over parts of Vilas
County (aided by lake-effect), 6 to 9 inches across the rest of
northern WI, and 4 to 6 inches farther south. With strong
northwest winds gusting to 35 to 50 mph inland, there is potential
for significant blowing and drifting snow, as well as tree damage
and power outages. The system winds down later Monday into Monday
night.

A clipper system passes north of the region Tuesday afternoon and
night, bringing a chance of snow followed by a surge of arctic air
for the New Year. This will bring renewed chances for lake-effect
snow in north central WI, as well as wind chills as low as 15 to
25 below zero later in the work week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 538 AM CST Sat Dec 27 2025

IFR/LIFR status covered the forecast area, with the exception of
the lakeshore, where MVFR ceilings were observed. Areas of fog and
freezing fog were reported over north central and central WI, with
vsbys mostly in the IFR/LIFR categories.

Low stratus (ranging from LIFR to MVFR) will persist through the
TAF period. Fog trends are a bit more problematic, as models are
quite pessimistic about significant improvement in vsbys. Suspect
there will be some improvement to MVFR/VFR during the late
morning and afternoon. Ceilings and vsbys should trend down again
after sunset, with periods of drizzle or very light rain
developing later in the evening and continuing overnight. Surface
temperatures should remain above freezing in most areas, so not
expecting any significant freezing precipitation tonight.

Southeast winds will gradually pick up today and continue into the
evening before diminishing. A brief period of borderline LLWS is
possible at the RHI TAF site later today, mainly from
20z/Sat-00z/Sun.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Sunday afternoon through Monday
afternoon for WIZ005-010-018.

Winter Storm Watch from Sunday evening through Monday afternoon
for WIZ011>013-019>021-031-037-045.

Winter Storm Watch from late Sunday night through Monday
afternoon for WIZ022-040-050.

Winter Storm Watch from Sunday afternoon through Monday morning
for WIZ030-035-036.

Winter Storm Watch from Sunday evening through Monday afternoon
for WIZ038-039-048-049-073-074.
&&

$$

DISCUSSION.....Kieckbusch
AVIATION.......Kieckbusch

NWS GRB Office Area Forecast Discussion