103
FXUS63 KGRB 291733
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1133 AM CST Mon Dec 29 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- A Blizzard Warning remains in effect for Door County until 9 am,
  otherwise Winter Storm Warnings continue for the rest of the
  forecast area today. Accumulating snow will taper off in most
  areas this morning, but strong winds and considerable blowing
  and drifting snow will persist during the day. Treacherous
  travel conditions are likely for the morning commute. Some tree
  damage and power outages may continue in northern WI and Door
  County.

- Strong northwest winds gusting to 35 to 50 mph inland, and gale
  or storm force gusts to 45 to 50 knots on Lake Michigan
  continue today, then gradually diminish this evening.

- A clipper system brings 1 to 2 inches of snow on Tuesday. This
  system will be followed by a surge of colder temperatures for
  the rest of the week. Wind chills as cold as 15 to 25 below zero
  are possible Thursday morning and Friday morning.

&&

.DISCUSSION...
Issued at 435 AM CST Mon Dec 29 2025

Powerful low pressure (around 980 mb) continued to move toward
southeast Ontario this morning. Widespread light to moderate snow
was observed over the forecast area, with the heaviest snow
occurring over the Fox Valley/lakeshore areas, where strong
forcing from a short-wave and mid-level FGEN was interacting with
a deep (100-150 mb) dendritic growth zone. Snow was tapering off
over parts of NC/C WI, except in the Lake Superior snow belt,
where a favorable NNW wind trajectory and increasing over-water
instability (Lake-H8 delta-t`s of 17+ C) was producing significant
lake-effect snow showers. Though strong wind gusts have not been
as persistent as expected early this morning, sporadic gusts to
32-40 knots have been reported at the ASOS sites, with 44 knots at
Gills Rock/Northport (northern Door County).

Winter Weather Headlines: No changes expected at this time. Most
of the accumulating snow will end from west to east between 4 am
and 8 am, though lake-effect snow showers will persist in north
central WI and northern Door County. Additional accumulations of
1/2 inch to 2 inches are expected in northern and eastern WI, with
slightly higher amounts possible in Vilas County due to lake-
effect. After the snow ends, headlines will be totally dependent
on the impacts of blowing/drifting snow. Wind gusts should
increase a bit early this morning, with widespread gusts to 35 to
45 mph, and up to 55 mph over northern Door County, so blowing and
drifting is still likely. The impact of blowing snow will not be
fully known until the morning commute, so any decisions to end or
downgrade headlines before their current expiration times will
have to wait until then. Door County observations are not
currently showing the required 1/4sm vsbys to validate the
Blizzard Warning, but would expect most of the problems would be
occurring over the far north part of the county. Unfortunately,
the vsby is currently missing on the Washington Island observation
and web cams at Gills Rock are snow covered. Power outage maps
show nearly 10K customers without power over northern WI, and this
is a bit lower than reports from earlier this morning. The
highest impacts are in Vilas County, where around 3500 customers
remain without power.

A clipper system will bring an inch or two of snow to the region
on Tuesday, followed by a surge of arctic air for the New Year.
This will result in an uptick in lake-effect snows in far north
central WI through midweek. Confidence remains high for wind
chill values to fall to 15 below to 25 below zero on Thursday
morning and Friday morning.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1133 AM CST Mon Dec 29 2025

Strong winds will remain in place for the early afternoon in the
wake of the departing winter storm. Periodic gusts up to 25-35
knots will likely keep blowing and drifting snow in place across
the region, which will hamper visibility for early in the TAF
period. Ceilings remain VFR for the early afternoon, but some
clearing will work its way in by the evening, which should bring
in some VFR ceilings for the overnight period.

The next round of snow showers is expected to arrive around midday
tomorrow, which will again feature some limited visibility and
lower ceilings to MVFR to start. Fortunately, this next system
should have significantly lower snow accumulations in store for
us.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 4 PM CST this afternoon for WIZ005.

Winter Weather Advisory until noon CST today for WIZ010-018>021-
030-031-035>037-045.

Winter Weather Advisory until 3 PM CST this afternoon for
WIZ011>013-038-039-048-049-073-074.

Winter Storm Warning until 6 PM CST this evening for WIZ022.

Winter Weather Advisory until 6 PM CST this evening for WIZ040-
050.
&&

$$

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

NWS GRB Office Area Forecast Discussion