427
FXUS63 KGRB 091702
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1102 AM CST Tue Dec 9 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

. Light snow ending early this morning. Even after the snow ends,
  freezing drizzle will remain possible through the morning.
  Slippery travel could occur for the morning commute.

- Winter Storm Warnings and Winter Weather Advisories issued for
  this evening into Wednesday morning. Heaviest snow, with rates
  over 1" per hour, expected in central WI this evening into the
  overnight hours. Snow ends late tonight over central WI and on
  Wednesday morning over eastern WI.

- Much colder temperatures arrive for the end of the week. Wind
  chills of -10 to -30 are possible Friday night into early
  Saturday and again Saturday night into Sunday morning.

&&

.DISCUSSION...
Issued at 324 AM CST Tue Dec 9 2025

Short Term...Today...Tonight...and Wednesday

First clipper of interest is spreading light to moderate snow from
west-to-east across the area early this morning. Based on upstream
obs and forecast soundings, ice stripping out aloft will lead to
freezing drizzle for a few hours after the snow ends. Based on
radar trends, steady snow ending over central WI will taper of in
the Fox Valley 10-11z (4-5am), and in Door County and the lakeshore
by 12z (6am). Where surfaces have been cleared of snow early this
morning and freezing drizzle is ongoing, untreated roads could be
slippery which will impact the morning commute. Once any lingering
freezing drizzle ends mid to late morning, expect a lull through
the afternoon. Nothing too notable in terms of winds or temperatures
today. Highs will reach the lower 20s north and into the upper
20s, even around 30 portions of central to east-central WI. Even
with this "warm- up" these readings will still be a bit below
average.

Late this afternoon, attention will be on potent clipper system
that will be riding strong 150+ kt upper jet across the northern
Plains into the western Great Lakes. Even at this short time
horizon, there are still significant differences in track of the
strong sub 990mb sfc low. Essentially many of the 00z CAMs,
including the 00z RAP/HRRR, favored swath of heaviest QPF/snow
over northern WI, while global models (ECMWF, GFS) were farther
south, though they had trended slightly north with this cycle.
NAM/Canadian represented compromise. Latest QPF trends and SLRs
in the 10-15:1 range, along with signal of heaviest 1hr QPF/snow
tapering as system shifts east (per HREF) resulted in upgrading
to a Winter Storm Warning for most of central WI (4-7" of snow),
but keeping that upgrade still west of the Fox Valley. Elsewhere,
a Winter Weather Advisory was issued for 2-5" of snow. If system
remains stronger farther east as especially the ECMWF and NBM
probabilities show (boosted by GFS and ECMWF ensembles), then an
additional upgrade would be needed across the Fox Valley and
possibly even toward the lakeshore. Does appear pretty certain
that bulk of heaviest snow from this system (rates possibly over
1.5"/hr for 2-3 hours) will occur this evening over central WI.
Snowfall rates elsewhere look to stay below 1"/hr with majority of
this occurring before daybreak on Wednesday as snow tapers off
from northwest to southeast.

Vilas County may be impacted by light lake enhanced snow as system
departs on Wednesday morning. However, the heaviest more impactful
snow from this should stay in area of stronger convergence closer
to Lake Superior.

North winds will be gusty on Wednesday, which will lead to some
drifting. Not sure extent of blowing as the snow will be wetter
type instead of powdery. Retained idea from previous shift that
where snow is heaviest there could be power outages due to the
increasing winds. Temperatures on Wednesday will be steady as the
low crosses, then fall off into the teens and lower 20s by late
day. Wind chills will be falling off into the lower single digits
in the afternoon over northern WI.

Long Term...Wednesday Night Through Monday

Focus of the long term forecast is the arrival of much colder
temperatures Wednesday through this weekend as well as another
possible round of snow Friday into Saturday.

Cold...Behind the departing cold front Wednesday colder air will rush
into the region Wednesday night with lows falling into the single
digits below zero away from the Lake Michigan. Highs Thursday and
Friday are only expected to rise into the middle to upper teens for
most locations. Friday night a second cold front is forecast to move
across the area bringing a blast of arctic air for the weekend.
Global ensembles show 850mb temps of  -18C to -24C overspreading the
region. With partial clearing Friday and Saturday nights
temperatures are forecast to fall into the single digits to teens
below zero with wind chills of -20F to -30F, coldest across central
WI. Will likely need cold weather headlines both nights for parts of
central and east-central WI. Lake induced clouds across northern WI
may keep apparent temperatures from falling to headline criteria.

Snow Chances Friday into Saturday...Another short-wave originating
over NW Canada is forecast to move through the northwest flow late
in the week, bringing another chance (40-60%) for accumulating snow
Friday into early Saturday morning. Snow totals are still highly
uncertain given the variability in the track of the short-wave. 01Z
NBM shows 30-40% probs for at least 1" of snow south of HWY 29 with
20-30% north to the UP border. With colder temperatures profiles and
deep saturation through the DGZ expect this snow to be more of a
powdery variety.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1102 AM CST Tue Dec 9 2025

A swath of snow will spread into central Wisconsin after 09.21Z
this afternoon and towards the lakeshore through 10.03Z.
The snow will diminish from the west prior to sunrise on
Wednesday. Visibility may be locally reduced under 1/2 SM at
times, particularly from central through east-central Wisconsin.
IFR/MVFR ceilings will persist through the period.

Southwest winds will shift easterly for a time tonight as low
pressure passes to the south. Northerly winds are then expected
on Wednesday with gusts of 20 to 30 kts.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 5 PM this afternoon to 6 AM CST
Wednesday for WIZ005-010-011-045.

Winter Weather Advisory from 8 PM this evening to 9 AM CST
Wednesday for WIZ012-013-022-038>040-048>050-073-074.

Winter Storm Warning from 5 PM this afternoon to 6 AM CST
Wednesday for WIZ018>021-030-031-035>037.
&&

$$

DISCUSSION.....JLA/GK
AVIATION.......JM

NWS GRB Office Area Forecast Discussion