NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 291148
AFDGRB

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

Updated aviation portion for 12Z 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 12Z TAF Issuance
Issued at 533 AM CST Mon Dec 29 2025

A potent winter storm is creating poor flying conditions across the
region early this morning, but conditions were improving from the
west as steady snow tapered off. Moderate to locally heavy snow
was still occurring over northern and eastern WI. Most locations
were reporting MVFR/IFR flight conditions, though some LIFR
conditions were observed over the far north and east. Strong
northwest winds were gusting to 30 to 40 knots, causing some
blowing/drifting of the snow.but

Snow will taper off outside of the lake-effect areas this morning,
but sporadic reductions in vsbys may linger into the early
afternoon due to blowing snow. A push of drier air should help
scatter out the low clouds late this afternoon, especially in the
northwest wind downslope areas of NE/EC WI. Lake-induced MVFR
stratus is expected to linger at RHI through this evening. Mid-
level clouds will increase ahead of an incoming clipper system
late tonight.

Strong northwest winds will continue through mid-afternoon, then
gradually diminish into the evening. LLWS will impact the TAF
sites this morning.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 3 PM CST this afternoon for WIZ005-
011>013-038-039-048-049-073-074.

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

Blizzard Warning until 9 AM CST this morning for WIZ022.

Winter Storm Warning from 9 AM this morning to 6 PM CST this
evening for WIZ022.

Winter Storm Warning until 6 PM CST this evening for WIZ040-050.
&&

$$

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