103
FXUS63 KGRB 090920
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
320 AM CST Sun Nov 9 2025

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Significant lake effect snow is expected across Vilas county
  today and tonight with 2 to 5 inches of accumulation possible
  (highest in the northwest of the county). Snowfall rates could
  exceed one inch per hour at times today.

- Snow showers, producing low visibility, are possible across
  north-central and central Wisconsin outside of the main lake
  effect belt this afternoon.

- Additional snowfall is also possible over the Door Peninsula,
  which may lower visibility briefly this morning through the
  early afternoon.

&&

.DISCUSSION...
Issued at 319 AM CST Sun Nov 9 2025

Short Term...Today...Tonight...and Monday

The main focus of the short term forecast will be on the snowfall
potential coming in from the north as a deep upper trough swings
through the region. While most of the region will likely see some
snow fall, the greatest impacts will be focused towards north-
central Wisconsin, with some additional snowfall possible across
the Door County Peninsula.

Snow Through the Afternoon...
Lake effect snow is expected to return to north- central
Wisconsin today as a strong upper shortwave drops into the region
through the morning to early afternoon hours. This cold airmass
will produce some fairly extreme lake effect snow parameters by
the late morning hours, with lake induced CAPE getting over 1000
J/kg, equilibrium levels near 18k feet, and delta-T values getting
to around 20 C by 850mb. This will allow for some organized snow
bands to push into north- central Wisconsin during the morning
hours, with some higher snowfall rates up to or possibly even
exceeding an inch an hour. The main limitation on snowfall will be
duration the bands remain in the region, as winds shifting from
northwest to north, which will shift the location(s) of where the
heaviest bands are situated. Still, would expected up to 2 to 4
inches across Vilas County through the afternoon, mainly focused
closer to the Upper Peninsula border in the northwest portion of
the county.

There will be a sharp gradient in the snowfall by the time you get
to Oneida County, with totals already dropping to around 1 to 2
inches for the Sunday later morning through early afternoon
period. Still, any decaying snow shower will still have the
potential to produce higher rates of snowfall for brief periods,
which may rapidly diminish visibility at times. Travelers should
be prepared for rapidly changing conditions, even if totals remain
much lower through central Wisconsin.

The aforementioned shortwave will also bring the potential for
additional snowfall along Door County as warm Bay waters help
enhance any persistent snow showers that made it across the Upper
Peninsula. The relatively short fetch of the Bay of Green Bay and
warmer surface temperatures sticking closer to freezing will help
limit the better snowfall potential (in contrast to north-central
Wisconsin), but intermittent snowfall will still be possible
through the morning to early afternoon hours, as evidenced by some
lake enhanced showers that already crossed the northern portions
of the county overnight. As a result, bumped up snow totals some,
with potential for up to 2 inches of snowfall through the day
today.

Snow through the Evening and on Monday...
The shortwave will have largely moved through the region by this
evening. As a result, while intermittent snow shower will remain
in the region for both north-central Wisconsin and the lakeshore,
additional totals are expected to be under an inch through the
early overnight. Snow departs most of the region by Monday
morning, but some intermittent snow showers will be possible over
Door County before dry conditions arrive Monday night. Additional
accumulations over Door County will still be possible, but
largely hampered by expected daytime temperatures getting back
into the middle to upper 30s during the daytime.

Temperatures...
Snow aside, today will be fairly cold day, with highs in the upper
20s across the north and getting into the lower to middle 30s
across the Fox Valley and lakeshore. Winds will be gusty through
the day, which will keep conditions feeling much colder,
especially this morning and again tonight where wind chill
readings will get into the low teens and possible single digits.
Monday will see temperatures a couple of degrees warmer, but will
likewise still feel relatively cold with wind chill readings
Monday morning still in the teens.

Long Term...Monday Night Through Saturday

After the current active winter weather into Monday, rest of the
forecast settles down. Warmer temps on the way late in the week
into next weekend.

Precipitation chances: Overall look minimal. May see a few flurries
late Monday night into early Tuesday as deep trough departs and
warm air advection aloft develops. Sfc low riding west to east,
well to the north of WI, will shift winds northwest Tuesday night
into Wed. Over-water instability/delta Ts just sufficient enough
for scattered light lake effect snow showers far north-central WI.
After this tapers late Wednesday, next chance of precipitation,
in the form of rain this time, will not occur until next weekend
with passage of stronger northern branch trough/sfc low crossing
central Canada.

Temperatures/Winds: 850mb/5kft AGL temps that start the week below
the 25th percentile for mid November climatology, flip back upward,
reaching over the 90th percentile by next weekend. Resulting highs
will reach normal by Thursday, then rise 5-10F above normal by next
weekend into the mid 50s. Winds could be gusty Tuesday/Wednesday
ahead of, and in wake of, the low pressure system crossing Canada.
NBM probabilities of 24hr gusts over 35 mph are highest on Tuesday
over eastern WI, then over all the area on Wednesday. These gusty
winds will likely result in conditions hazardous for small craft
on the waters.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1033 PM CST Sat Nov 8 2025

A clipper system moving away from the area will bring an end to
the light snow across central and east-central WI (south of KATW)
around 06z Sunday. Meanwhile, lake effect snow showers will
continue into early Sunday morning before there will be a lull
towards the 12z. Low level winds over Lake Superior will become
more favorable for lake effect snow showers (50-90%) to become
more widespread and more intense across north-central Wisconsin
late Sunday morning and through Sunday afternoon. Some of the
heavier snow showers could reduce visibilities and CIGS into the
IFR/MVFR category. The most impacted TAF site will be KRHI where
an accumulating snow is expected. Gusty north/northwest winds can
be expected overnight through Sunday afternoon, with the strongest
gusts of 20-25 knots expected during the day. Lake effect snow
showers will gradually taper off Sunday night, except across the
far north north where snow will linger into Monday.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM CST Monday for WIZ005.

Winter Weather Advisory from 9 AM this morning to 6 PM CST this
evening for WIZ010.
&&

$$

DISCUSSION.....Uhlmann/JLA
AVIATION.......Eckberg

NWS GRB Office Area Forecast Discussion