NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 231701
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1101 AM CST Tue Dec 23 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Several rounds of wintry precipitation will be possible on
  Wednesday. The first round will be north of Hwy 29 Wednesday
  morning, with the second round south of Hwy 29 Wednesday
  evening.

- Above normal temperatures are expected throughout the work
  week, with highs expected to read above freezing.

- Confidence is increasing for a more widespread round of mixed
  wintry precipitation Thursday evening into Friday. Travel
  impacts will be possible.

&&

.DISCUSSION...
Issued at 221 AM CST Tue Dec 23 2025

Precip chances... Any remnants of drizzle/freezing drizzle have
exited to the east early this morning as drier air works in from
the west. Canadian high pressure then encroaches from the north
later this morning, offering us a brief dry spell. A ridge-riding
shortwave pulse then brings additional chances for freezing
drizzle/wintry precipitation on Wednesday, with signs pointing
toward another sneaky event. Two target areas are coming into
focus: the first round north of Highway 29 Wednesday morning in
conjunction with the shortwave and the second round south of
Highway 29 with better saturation. Snow will likely be the
dominant p-type across the north where temperatures stay below
freezing, whereas rain is favored for the southern activity.
Freezing drizzle will be prone to mix in near/around the Highway
29 corridor Wednesday evening as temps fall below freezing,
offering up a similar setup for yesterday's messy freezing precip
event.

Forecast concerns gradually shift to potential for a messy mixed
precip event Thursday into Friday, which would pose a hazard to
post-holiday travel. Warmer temperatures aloft would favor
predominantly liquid precip, though surface temperature behavior
would determine whether we see rain versus freezing rain. Driving
low pressure initially doesn't look too impressive as it treks
across the northern Plains late Thursday, with upper-level
dynamics somewhat lacking. Surface wave eventually reaches
Wisconsin early Friday morning, with ensemble cluster analysis
showing two axes of heavier QPF that split northeast Wisconsin to
the north and south. However, beginning to see a signal emerge for
an inverted trough setup early Friday morning, which would
enhance precip potential. As such, starting to see a trend toward
some QPF sneaking up into east-central Wisconsin Thursday night
into Friday. Probabilistic guidance offers a more pessimistic
scenario, showing a widespread 60 to 90% chance of receiving
frozen precip, mainly north of Hwy 29. Will have to see if this
trend holds over the next several forecast cycles.

Temperatures... Strong signal still present for above average
temperatures through at least the end of the work week as
positive height anomalies and mild Pacific flow usher in an above
freezing airmass. Highs will plateau in the mid to upper 30s
Friday and Saturday, with areas in/around the Fox Valley flirting
with 40 degrees. Dewpoints likewise rise above freezing beginning
Christmas Eve, which may result in widespread fog/low cloud
development. Post-holiday travel may be impacted as fog potential
lingers beyond Christmas Day, especially in areas that receive any
precip. Temperatures then crash on Sunday as an arctic cold front
passes over the Great Lakes.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1101 AM CST Tue Dec 23 2025

Primary concerns in the short term involve LLWS this afternoon
and potential for light frozen precipitation and fog late tonight.

Low level wind shear will impact KRHI/KAUW/KCWA through
approximately 23z as a 35-40 kt jet persists at 2000 ft agl. At
the surface, gusty west to northwest winds to 20 kts will subside
early this evening as high pressure builds in and winds become
light/variable.

A brief period of low MVFR ceilings (1100-1400 ft agl) could move
into north- central WI for a time this afternoon. Otherwise, mainly
VFR conditions prevail through the evening with passing mid and
high clouds.

However, low level moisture increases overnight as warm advection
arrives aloft. Guidance suggests a period of fog and low stratus
development at KRHI after 08z, with visibilities potentially
dropping to 1-2SM and ceilings to LIFR/IFR. Added a tempo group
for the KRHI TAFs. Additionally, a brief 1-2 hour window of light
snow or freezing drizzle is possible near the U.P. border early
Wednesday morning, though dry air below 800mb may limit
accumulation. Confidence remains low enough to exclude a mention
at the KRHI TAFs.

Confidence is high for VFR conditions elsewhere through 18z
Wednesday.

Outlook: MVFR ceilings and potential for a light drizzle will move
into central and east-central WI late Wednesday afternoon into the
evening.

&&

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

&&

$$

DISCUSSION.....Goodin
AVIATION.......MPC