096
FXUS63 KGRB 091618
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1018 AM CST Sun Nov 9 2025

New Information added to update section.

.UPDATE...
Issued at 1017 AM CST Sun Nov 9 2025

The intense snow band continues into the Door Peninsula, though
with a slight shift to the west. The band is approaching Sturgeon
Bay late this morning, but remains steady into Sister Bay and
Ephraim. Just received a report of 5 inches in Jacksonport along
with 1 inch per hour snowfall rates. Although the axis of the band
may yet shift slightly, the high snowfall rates combined with
reports approaching warning criteria, and favorable conditions for
lake effect through the end of the afternoon has prompted an
upgrade to a Winter Storm Warning until 6 pm today.

PREVIOUS UPDATE
Issued at 810 AM CST Sun Nov 9 2025

Upstream preconditioning over eastern Lake Superior combined with
convergent flow over the central Upper Peninsula is support a
strong snow band into northern Door County. Just received a report
of 2.5 inches of accumulations at Jacksonport. The snow band will
be capable of producing 1 inch per hour snowfall rates. While
slight wind directions changes are possible, guidance shows
sfc-850mb winds are pretty locked in through late afternoon with
strong synoptic support pushing in from the north.

As a result, issued Winter Weather Advisory for Door County until
6 pm this evening. Went with local amounts up to 5 inches, but
this may be conservative if this snow band remains locked into
Ephraim.

&&

.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 12Z TAF Issuance
Issued at 535 AM CST Sun Nov 9 2025

Lake effect snow showers are expected to return in the mid to late
morning hours to north-central Wisconsin, bringing some MVFR
ceilings and possibly intermittent IFR visibility to RHI. As
these showers move further southwards into central Wisconsin, they
should lose some of their intensity but may still impact aviation
at AUW and CWA at times. Along the lakeshore, lake effect snow
bands will still be over Lake Michigan but may move onshore for
brief periods in the afternoon. Confidence on this and timing is
lower, so kept mention to a PROB30 group for GRB, ATW, and MTW for
now. Snow potential is expected to decrease as we get into the
overnight period tonight.

Snow aside, winds will be gusty through the period, with periodic
gusts up to 20 knots expected across the area, mainly out of the
north.

&&

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

Winter Weather Advisory until 6 PM CST this evening for WIZ010.

Winter Storm Warning until 6 PM CST this evening for WIZ022.
&&

$$

UPDATE.........MPC
DISCUSSION.....Uhlmann/JLA
AVIATION.......Uhlmann