024
FXUS63 KGRB 072354
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
554 PM CST Fri Feb 7 2025

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Hazardous winter travel is expected after midnight tonight
  through Saturday evening due to a widespread accumulating
  snowfall. There is a 50-70% chance of snowfall accumulations
  greater than 6 inches along the Highway 29 corridor from Wausau
  to Green Bay and a 70-100% chance for 2+ inches. Winter Weather
  Advisories have been issued for all of north-central and
  northeast Wisconsin.

- Bitterly cold wind chills from 5 below to 20 below zero will be possible
  Monday, Tuesday, and Wednesday night, with the coldest values
  over central and north-central Wisconsin.

&&

.DISCUSSION...
Issued at 142 PM CST Fri Feb 7 2025

Short Term...Tonight and Saturday

Focus of the short-term forecast remains snowfall chances late this
evening through Saturday. A Pacific wave that is currently over
northwest Montana will continues to propagate through progressive
flow this evening, arriving to central WI around midnight. CAMs show
an area of light snow associated with mid-level f-gen developing
over central WI ahead to the main wave of snow. This initial push of
snow may lead to a localized band of 2-3" of snow from Wausau to
north of Green Bay by daybreak Saturday. Snow will then become more
widespread Saturday morning as the main short-wave and LFQ arrive.
Forecast thermal profiles Saturday morning through early afternoon
look favorable for efficient dendritic grow along the highway 29
corridor as f-gen is maximized through a saturated DGZ. It`s along
this general corridor that the highest snowfall totals of 4-8" are
expected with a few localized amounts possible up to 9-10" possible.
Probs for greater than 6" of snow within this band remain in the 50-
70% range. Further north the strongest f-gen appears to be above the
DGZ which may result in less efficient snow growth and lower totals
of 2-5". Areas south of highway 10 look to be along a sharp gradient
 in snowfall amounts with 3-6" possible to the north and 1-3" to the
south. A huge caveat here is if the main band of snow shifts slight
north or south areas on the current periphery may see drastically
different amounts that currently forecast.

One consistent detail over the past 24 hours is a quicker end to the
snow than forecast earlier in the week. Expect snow be done by mid
to late afternoon for much of northern and central WI. Snow should
then come to an end during the early evening in east-central and far
north-east WI.

With the level of uncertainty in where the heaviest snowfall will
develop decided to upgrade the Winter Storm Watch to a Winter
Weather Advisory for the entire forecast area. Later shifts may be
able to upgrade a row or two of counties to a Winter Storm Warning
as it become more apparent where the main snowband will develop.
Another deciding factor in going with a Winter Weather Advisory over
a Winter Storm Warning at this time is the lake of "nudgers" with
this system. Given the Saturday timeframe roads should not be as busy
with few morning or evening commuters. Winds or temperatures are
also not expected to be big factors with this system as wind gusts
peak around 10-15 mph and temperatures will range from the middle
teens to upper 20s across the region.

Long Term...Saturday Night Through Friday

Generally, weather impacts will be low over the next week once
the snow departs on Saturday night. Potential impacts could
include cold wind chills and light snow chances.

Cold wind chills: Arctic high pressure will be building into the
area from Sunday through Wednesday. The pressure gradient will
likely be sufficient to create wind chills from 10 below to 20
below zero over north-central to central WI on Monday night into
Tuesday morning. Very cold nights are expected with lows below
zero away from Lake Michigan on Tuesday night and Wednesday night.
But with the arctic high directly overhead, winds will likely
decouple which will mitigate the risk of dangerous wind chills. As
it stands, wind chills do not look cold enough to necessitate
cold weather headlines.

Light snow chances: A moisture starved reinforcing arctic front
could create light snow on Monday night. Precipitable water values
are only 50-60% of normal, so cannot see much more than a dusting
of fluff if accumulations occur.

Another chance of light snow could occur on the very back edge of
a storm system moving across the Ohio Valley on late Wednesday
into Thursday. Eastern WI will have the highest chances of snow,
but again, probabilities of accumulations 1 inch or greater are
sub-20%.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 554 PM CST Fri Feb 7 2025

Good flying conditions will likely last into the evening and
portions of the early overnight, especially in eastern Wisconsin.
Conditions then deteriorate early Saturday morning as snow begins
to spread into the region from west to east. Low ceilings and
visibility are expected as the snowfall spreads into the region,
with the heaviest snowfall still expected generally along and
north of the Highway 29 corridor between AUW and GRB. The peak of
the snowfall will likely occur in the late morning through the
mid afternoon. Visibility and ceilings during this time will
likely drop to MVFR to IFR at times. Conditions will then improve
again from west to east around the end of the TAF period Saturday
evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight tonight to 9 PM CST
Saturday for WIZ005-010-018>020-030-035-036.

Winter Weather Advisory from 3 AM Saturday to midnight CST
Saturday night for WIZ011>013-021-022-073-074.

Winter Weather Advisory from 3 AM to 9 PM CST Saturday for
WIZ031-037>040-045-048>050.
&&

$$

DISCUSSION.....GK/MPC
AVIATION.......Uhlmann