NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 220451
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1051 PM CST Sun Dec 21 2025

Updated aviation portion for 06Z TAF issuance

.UPDATE...
Issued at 950 PM CST Sun Dec 21 2025

Have noted minor shift southward in the 18z/00z guidance with
expected mid-level frontogenetic snow band. Now appears the axis
of snow impacts the highway 29 corridor, starting 5-6a and lasting
through 9-10a. Snowfall rates up to 0.5" per hour will impact the
Monday morning commute. Band is transient and SLRs lower at 8-10:1,
so still think overall snow totals will end up in the 1-2" range,
though it is not out of the question snowfall in the narrowest
band ends up more in 2-3" range. Forecast soundings still indicate
warm layer centered at 925mb. Greatest risk of this is from
Waushara County into southern Fox Valley and east to the lakeshore.
There is also still potential the precip will try to end from the
south as ice aloft is stripped away. Given the light snow, potential
mix all coming together for the morning commute, issued SPS to give
those traveling to work/school a heads-up the morning commute could
be slippery and slow.

&&

.KEY MESSAGES...

- Round of snow will spread into the region late tonight into
  Monday morning. A narrow swath of 1-3" is possible along and
  north of HWY 29 into Door Co. Lesser amounts under 1" further
  north and south. lingering precipitation may see a brief wintry
  mix during the afternoon hours Monday.

- Above normal temperatures expected through the work week.

&&

.DISCUSSION...
Issued at 119 PM CST Sun Dec 21 2025

Rest of Today...

Quiet conditions will remain to close out the weekend. Mid-level
clouds streaming over the region should clear out this evening
leaving mostly clear skies. Temperaturs in the teens to low 20s
across the region this afternoon may cool a few degrees after
sunset, however, as warm air advection strengthens overnight
temperatures will rise.

Monday Snow Chances...

CAMs show snow blossoming shortly after midnight tonight across
central WI as a left entrance region arrives to support ascent
associated with low and mid level warm air advection and a
developing LLJ. Forecast soundings support snow being the dominate p-
type during the onset of this event for much of the region, however,
a weak warm nose could lead to isolated pockets of snow mixed
with freezing rain across central WI. As profiles saturate the
risk for freezing rain diminishes through Monday morning. A band
of moderate snowfall (up to 0.5" per hour) is expected to be
focused along an area of mid-level f-gen stretching from central
to far northeast WI. Timing of those higher snowfall rates is
generally expected between 6AM and Noon. Accumulations are
expected to be greatest (1-3") withing a narrow corridor generally
along and north of HWY29 into Door Co. Lesser amounts, under 1"
are expected across the Fox Valley and north of HWY 8. Impacts
from this event may be slightly increased due to the timing of the
heaviest snow coinciding with the Monday AM commute. If you are
commuting Monday morning give yourself extra time to reach your
destination.

As moisture gets stripped out of the column Monday afternoon there
may be a brief window for freezing drizzle to develop across east-
central WI. However, with any freezing drizzle falling on fresh snow
or treated roads impacts should be minimized. Any untreated roads
could see a few isolated slippery spots impact the Monday PM
commute.


Mild conditions rest of the week...

Height rises behind the departing snow will usher seasonally warm
temperatures back into the region beginning Tuesday. With upper-level
flow then becoming more zonal through the middle of the week
temperatures will likely run 5-10 degrees warmer with highs in the
middle to upper 30s through the end of the week.

GEFS/ENS hint at another chance for widespread precipitation coming
later in the week as the next trough digs into the western Great
Lakes. ENS soundings and meteograms show the potential for this to be
a messy mixed precipitation event across the northern half of
Wisconsin. However, cluster analysis of 500mb global ensembles flow
fields shows the pattern beginning to diverge significantly toward
the end of next week and into next weekend which is leading to low
forecast confidence for this period at this time. Will need to watch
this period closely as a messy mixed precipitation event would
impact post Christmas travel.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1050 PM CST Sun Dec 21 2025

VFR conditions into the overnight with thickening mid clouds from
the southwest. Strengthening winds just above the surface will
create LLWS at all the TAF sites through Monday morning.

A round of snow will move north into central WI late tonight and
continue spreading north through late Monday morning, before shifting
east and ending. Cigs will drop to MVFR as the snow moves through,
with IFR over central and north-central WI. Expect a 2-4hr period
of light to moderate snow with IFR visibility for all sites except
RHI and MTW. Once the snow ends, a mix of MVFR to low-end VFR cigs
will linger over the region.

For ground operations snow accumulations of around 1" are expected
at most terminals Monday morning, however, a narrow swath of 1-3"
is possible along and north of a CWA to GRB line.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE.........JLA
DISCUSSION.....GK
AVIATION.......JLA