260
FXUS63 KGRB 180440
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1040 PM CST Mon Nov 17 2025

Updated aviation portion for 06Z TAF issuance

.UPDATE...
Issued at 935 PM CST Mon Nov 17 2025

Scattered rain is just starting to work into southwest WI, with
more concentrated precip upstream over MN and IA (lightning
strikes noted earlier). No snow is seen in obs upstream yet.
Probably will see no obs of snow into WI until after midnight.
Overall, no big changes to expected arrival time of precip (brief
rain/snow mix to snow) into central WI after midnight, with
steadier snow (in mid-level Fgen band) spreading into much of
central WI south of highway 10 after 3 am Tuesday. Latest snow
forecasts through late Tuesday morning not too different from
earlier, with 1-3" south of highway 10 in Wood, Portage, Waupaca
into Waushara.

Most models insistent that dry air present over northeast WI
closer to nearby high pressure will restrict the northern and
eastern edges for accumulating snow with this event. HRRR has
been locked onto this for many runs now and is joined by latest
RAP and Canadian. NAM, which has been inconsistent with its heavy
snow axis over the last two days, is opposed as it shows the
heaviest snow band farther north. HREF slowly rolling in, but
looks in line with the majority of guidance, keeping most notable
accums south of highway 10. All this to say, no changes will be
made to the going Winter Weather Advisory. Debated on adding
Winnebago for Oshkosh area and the morning commute/first snowfall,
but given latest amounts are only around 1", will let that be
decided overnight once trends become more apparent. At the least
could see SPS.

&&

.KEY MESSAGES...

- Light to moderate snow late tonight into Tuesday morning across
  the south with accumulations of 1 to 3 inches. A Winter Weather
  Advisory has been issued for central Wisconsin west of the Fox
  Valley.

- The Fox Valley could see up to an inch of snow with lesser
  amounts across the rest of central Wisconsin not in the advisory
  and east-central Wisconsin. North-central and northeast
  Wisconsin will be mainly dry.

- Another low pressure system will bring precip chances (30-60%)
  Thursday, mainly in the form of rain.

- Temperatures remain pretty seasonal through the week.

&&

.DISCUSSION...
Issued at 150 PM CST Mon Nov 17 2025

Snowfall amounts tonight into Tuesday: Models have come into
better agreement and made a shift to the north with the band of
FGEN late tonight into Tuesday morning. In addition, the hi-res
models are now sampling this system and are coming into better
agreement with the northward shift. HREF probabilities of
exceeding 1 inch of snow is now around 50% across the Fox Valley
from Appleton south to Oshkosh with 70-80% west of this area. The
following probabilities are currently progged across central
Wisconsin west of Appleton and Oshkosh and south of Marshfield
late tonight into Tuesday morning:

- 50-70% of exceeding 2 inches
- 30-50% of exceeding 3 inches
- 10-30% of exceeding 4 inches

Given these probabilities the most likely snowfall amounts across
this area is expected to be 1 to 3 inches, with snowfall amounts
up to 4 inches possible (75th percentile) and the worst case
scenario of 5 inches (90th percentile). The timing of this snow,
during the morning commute on Tuesday, adds a layer of complexity
as the impact will likely be higher even if snowfall amounts come
in on the lower end. Given the impacts of the first accumulating
snow of the season during the morning commute will issue a Winter
Weather Advisory for Waushara, Wood, Portage, and Waupaca counties
from late tonight through Tuesday morning. The compact nature of
frontogenesis means snowfall amounts will be in a tight gradient
with southern portions of Wood, Portage, and Waupaca counties
likely receiving more snow than the northern portion of those
counties.

The rest of the forecast area will range from completely dry
across north-central Wisconsin, to a mix of rain and snow across
east-central Wisconsin north and east of the Fox Vally and some
light snow across central Wisconsin north of the main FGEN band.
Snowfall amounts outside of the main band are expected to mainly
be below an inch given abundant dry air in place and the lack of
forcing.

Rest of the forecast: Dry conditions will prevail on Wednesday as
high pressure drifts over the Great Lakes. Next chance (40-70%)
for precip arrives Thursday as a clipper-like system races across
southern Canada. While the best moisture and dynamics will be
north of the area, some WAA, a shortwave trough, along with a weak
frontal boundary, will move across the area to produce some
precip. Amounts are looking on the light side, with probabilities
of 0.25"+ under 25%. Looking like mainly rain, but a little snow
could mix in over the north. Ensembles have really backed off on
bringing a more moisture rich, wrapped-up system for Friday into
Saturday, so unfortunately prospects for any substantial rain now
looks low.

Temperatures & Winds: Temps will remain pretty close to normal
for the first half of the week, with highs mainly in the upper
30s to mid 40s and lows in the upper teens and 20s (slightly
warmer near Lake Michigan). A brief shot WAA will give a small
bump in temps on Thursday with highs in the mid and upper 40s for
most locations. We could get a 50 in the south, but probabilities
of reaching 50 remain under 20% due to cloud cover. Winds will be
much lighter today and for the majority of the week, with gusts
only reaching up to 15 mph.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1039 PM CST Mon Nov 17 2025

VFR with mid and high clouds late this evening, but late tonight
clouds will lower from central to east-central WI, while skies
stay mostly clear over the north. MVFR clouds and light snow (IFR-
MVFR vsby) will then steadily work across areas to the south of
highway 29 on Tuesday morning. The terminal with greatest chance
to see IFR vsby will be ATW for a few hours on Tuesday morning as
northern edge of snow band moves across. CWA, GRB and MTW will
only be on edge of steadier snow, while dry conditions prevail at
AUW and RHI. Snow will eventually mix with and change to light
rain by midday, before ending. All areas will be back to VFR
by late Tuesday afternoon as the system exits the region.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 2 AM to noon CST Tuesday for
WIZ035>037-045.
&&

$$

UPDATE.........JLA
DISCUSSION.....Kurimski
AVIATION.......JLA