Green Bay, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

060
FXUS63 KGRB 180454
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1054 PM CST Fri Jan 17 2025

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- An arctic airmass arrives this weekend, bringing a prolonged
  period of wind chills of 20 to 35 below zero from Saturday
  night through Wednesday morning. Wind chills as cold as 40 below
  are possible on Tuesday morning.

&&

.DISCUSSION...
Issued at 353 PM CST Fri Jan 17 2025

Short Term...Tonight and Saturday

Weak forcing ahead of a surface front a mid-level shortwave is
showing some weak precip returns on radar from southeast MN into
north- central WI. However, little, if any, of this is reaching
the ground. Flurries/sprinkles or a brief, light shower are
possible throughout the afternoon and early evening, but most
places will remain precip-free. Winds at 1930Z were from the W
and SW, but continue to veer NW. This will bring chances of on/off
lake effect snow showers to far north-central Wisconsin starting
this evening. Amounts here will be light, with up to 1" of
accumulation from 00Z/Sat to 00Z/Sun.

As the winds turn NW, this also begins the change to a much
colder airmass. Temperatures at 1930Z were in the middle 30s to
lower 40s, with Waupaca coming in at 45 and Wautoma 46 degrees.
Expect to see readings about 25-40 degrees cooler by Saturday
morning. Temps will remain fairly steady throughout Saturday, but
gusty NW winds will lead to wind chills below zero for the most
part, and teens below zero in central/north-central WI. Readings
will get much colder into Saturday night.

Long Term...Saturday Night Through Friday

Main focus from this forecast period is the continued strong signal
for bitter cold temperatures and dangerously cold wind chills
associated with an arctic airmass. The coldest conditions will occur
between Saturday night through Wednesday morning. In addition to the
cold, periods of light lake-effect snow showers are anticipated in
far north-central WI, but impacts will be minor.

Temperatures...An anomalously cold airmass will overspread the
region from Saturday night through Wednesday morning. Despite this
airmass being abnormally cold for this time of year, air
temperatures will not be nearing/threatening records. However, high
temperatures will be in the single digits above and below zero each
day from Sunday through Tuesday. Low temperatures will be about 20
to 25 degrees below normal each night/morning from Saturday night
through Tuesday night with lows ranging mainly from -10 to -25F.
Slightly "warmer" air returns to the region on Wednesday as a
surface ridge builds over the area.

Wind Chills...A prevailing northwest wind will combine with the
bitter cold temperatures and generate dangerously cold wind chills.
The coldest wind chills are expected during the overnight into
morning hours each day. Due to temperatures decreasing slightly and
surface winds increasing slightly, wind chill values have decreased
for Saturday night into Sunday. Therefore, decided to move forward
with issuing a Cold Weather Advisory starting Saturday evening. See
the next section for more details on headlines. Will continue to
monitor the need for an Extreme Cold Warning for early next week as
the probability of wind chills of -30 or colder is greatest Monday
morning (roughly 40-80%) and Tuesday morning (70-100%).

Cold Weather Headlines...After collaboration with surrounding
offices, have issued a Cold Weather Advisory from Saturday evening
through Monday evening. Decided to have the advisory continue during
the afternoon hours, despite the possible brief window of wind
chills rising above criteria. An Extreme Cold Warning will likely be
needed from Monday evening through Tuesday morning, but will allow
subsequent shifts to analyze the forecast closer. An additional Cold
Weather Advisory may be needed for Tuesday afternoon through
Wednesday morning.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1045 PM CST Fri Jan 17 2025

A cold front had moved through the forecast area by late evening,
and low clouds between 2500-5000 ft AGL had overspread all but
the far southeast portion. Snow showers were ongoing over far NC
WI, and flurries were reported elsewhere. Northwest winds were
gusting to 20-30 kts.

Low clouds, with MVFR ceilings in parts of NC/C WI, will continue
across the region until clearing arrives Saturday morning/early
afternoon. The low clouds will persist longer north of RHI, and
lake-effect snow showers will likely continue in northern Vilas
County through Saturday evening. Gusty northwest winds will
continue through Saturday morning then diminish a bit during the
afternoon and evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Cold Weather Advisory from 9 PM Saturday to 9 PM CST Monday for
WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074.
&&

$$

DISCUSSION.....KLJ/Kruk
AVIATION.......Kieckbusch