341
FXUS63 KGRB 231631
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1031 AM CST Mon Dec 23 2024

New Information added to update section

.UPDATE...
Issued at 1022 AM CST Mon Dec 23 2024

Have cancelled the advisory over the northwest part of the
forecast area, where little impacts were reported. Kept the
advisory farther south, where light snow and patchy light freezing
rain/drizzle was being reported. Have shifted the focus for the
most significant impacts across the southern part of the forecast
area, where a band of moderate snow (1-3 inches) is expected to
set up during the afternoon. This band may cause significant
travel hazards for the afternoon commute from the southern Fox
Valley to Manitowoc County.

&&

.KEY MESSAGES...

- A Winter Weather Advisory remains in effect for central,
  northeast and east central WI through this afternoon. The most
  hazardous travel conditions are anticipated across the southern
  part of the forecast area, where a band of moderate snow sets up
  and impacts the late day commute.

- A warming trend is anticipated this week, with temperatures
  about 15 degrees above normal by late this week.

- Widespread rain chances return late this week.

&&

.DISCUSSION...
Issued at 319 AM CST Mon Dec 23 2024

Short Term...Today...Tonight...and Tuesday

A low pressure system will track through southern Wisconsin today,
then southern lower Michigan this evening. The low itself will
have plenty of dynamics with northern Wisconsin under the left
exit region of an upper level jet as a potent mid-level PV anomaly
moves through the western Great Lakes. Despite the decent
dynamics, moisture will be at a premium as model soundings show
quite a bit of dry air in place in the mid levels. This dry air
will mean fairly narrow bands of precipitation along with
freezing drizzle at times as ice crystals will have difficulty
maintaining themselves in the column. The main time periods for
freezing drizzle appear to be this morning as the column moistens
up and the afternoon/evening as the low pulls away. Once the
column moistens up hi-res models do show a swath of light snowfall
across the region today; however, there are still differences
regarding the placement of this swath. There are some models that
keep the swath north, some south, and some in between.

The heaviest swath of snow looks to accumulate 1 inch (30-50%
probability), with up to 2 inches possible (20-30% probability),
and locally higher amounts of 3 inches (10-15% probability). The
main snow swath right now appears to be somewhere south of highway
8 and north of highway 10 with the caveat of a shift north or
south. The freezing drizzle is expected to produce a light glaze
of ice of a few hundredths of an inch. Given the impact from a
few inches of snow and freezing drizzle, will maintain the Winter
Weather Advisory as driving conditions could be hazardous for the
expected busy travel day along with the expected commutes.

Conditions should improve tonight as the low and associated
precipitation head east of the area with dry weather expected on
Tuesday as a ridge of high pressure builds in across the region.

Long Term...Tuesday Night Through Sunday

Main highlights from this forecast period revolve around the
potential for precipitation sometime later this week and
prevailing above normal temperatures.

Precipitation...Moisture from a southern stream system will
attempt to lift north on Wednesday (Christmas Day) along the
Mississippi Valley into the Upper Midwest, but will struggle and
run into a ridge of dry air over the region. This will lead to dry
conditions for Christmas Day across the forecast area, but
prevailing low-level moisture may lead to a cloudy day.

Beyond Wednesday (Christmas Day), models are still in agreement with
the forecast area seeing precip at times from Thursday through the
weekend as a southern stream system lifts into the area. Although
there are timing and placement differences, there appears to be
better agreement for the greatest chance for widespread precip
occurring from Friday into Saturday. Anticipate any of these precip
would be in the form of rain due to a prevailing warmer airmass, and
therefore, impacts would be minimal.

Temperatures...Above normal temperatures are expected for the long-
term forecast, with the potential to see highs in the 40s by late
this week. Despite these temps being about 15 degrees above normal,
these values will not near record values. However, the combination
of areas with a snow pack and the warmer temperatures overnight, may
lead to some periods of foggy conditions.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 623 AM CST Mon Dec 23 2024

Conditions will rapidly deteriorate this morning to MVFR/IFR as a
low pressure system tracks through southern Wisconsin and brings
precipitation to the region. Initially precipitation will include
light freezing drizzle or mixed light snow/freezing drizzle early
before transitioning over to light snow this morning. Snow
accumulations through this afternoon may be around an inch or
two, with a higher band up to 3 from Wausau to Oconto. Any snow
will impact visibility for the TAF period. Precipitation then
pulls out of the region this evening with dry conditions expected
overnight and improvement to VFR across the Fox Valley.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 3 PM CST this afternoon for WIZ013-
020>022-030-031-035>037-045-073-074.

Winter Weather Advisory until 6 PM CST this evening for
WIZ038>040-048>050.
&&

$$

UPDATE.........Kieckbusch
DISCUSSION.....Kurimski/Kruk
AVIATION.......Kurimski