977
FXUS63 KGRB 121135
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
535 AM CST Thu Nov 12 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Intermittent lake effect snow showers are expected across north-
  central Wisconsin Thursday through Friday night. Accumulations
  have a 30% chance of exceeding 2 inches of snowfall.

- There is a 30% chance lake effect showers also turn inland off
  Lake Michigan into Door and Kewaunee Counties. If this occurs,
  impactful accumulating snow will be possible in these areas
  Friday morning as well.

- Mainly dry this weekend with a slow warming trend into early
  next week.

&&

.DISCUSSION...
Issued at 1147 PM CST Wed Nov 11 2026

Lake Effect Showers Across Northern Wisconsin...

Continued cold air advection from the north will bring lake
effect snow showers into the region Thursday through Friday night.
How far inland these showers get throughout the day Thursday and
Friday will vary, but the majority of any accumulations will be
across north- central Vilas County, with only trace to dusting
amounts making their way further inland. Accumulations will be
primarily limited during the day by above freezing surface
temperatures and winds, so although a few inches of snowfall are
in the forecast, actual surface accumulation probabilities are
lower, with around 30% chance of exceeding 2 inches of snowfall
across Vilas County. If snow accumulation proves more robust (10%
worst case), accumulations could get up to 3 to 4 inches over the
course of the 48 hour period.

Lake Effect for Lake Michigan...

Lake effect showers will also be underway over Lake michigan as
the northerly winds increase. The main areas to watch will be Door
and Kewaunee counties, which may see a rapid increase in
precipitation if these showers get enough of an easterly
component to them to bring the banded snowfall onshore. These
areas are also unlikely to see snow mix in until the overnight
period late tonight, with pure snow likely after midnight. That
said, if this band does move inland overnight, impactful snowfall
could be in the works for portions of Door and northern Kewaunee
counties. Lake induced CAPE around 200-300 J/kg, Delta-T around 15
degrees, and good mixing through the lowest layer near the lake
surface would all support concern for a push of higher snow totals
over a relatively localized area, as lake effect snow bands are
typically quite narrow. In the current 10% worst case, this could
bring a faster 4+ inches in 12 hours, which would merit the first
Winter Weather Advisory of the season. Confidence of all this
lining up is increasing over the last couple forecast cycles but
still only sits at around 30% on the probabilistic side, as
p-types over Door do switch back to rain during the latter part of
the day Friday. Therefore, will hold off on any headlines at this
juncture, but where the radar returns over Lake Michigan and the
Bay of Green Bay orient themselves over the next 24 hours will be
important to monitor.

Further Inland...

The rest of the region may see some sprinkles or even flurries at
times, with the flurries more likely during the overnight period
Thursday night into Friday morning as the air column gets colder.
First possible snowflakes region-wide aside, impacts for the rest
of the region will be fairly minimal.

Rest of the Forecast...

Quiet conditions are expected to return to the region over the
weekend. High temperatures that will be near normal Thursday and
Friday will see a slow rise going into next week, getting back
towards the 50s across the region.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 535 AM CST Thu Nov 12 2026

A mix of VFR and MVFR conditions exist across the region to start
the TAF period as lake induced status clouds are expanding
southward across northern WI, while an area of clearing works east
over far northeast and toward east central WI. The MVFR cigs will
likely fill in to some extend through the morning, however, status
may remain scattered enough at times to keep VFR conditions across
east-central WI for much of the morning. The main aviation challenge
through the TAF period will be periods of lake effect rain and show
showers coming off both Lake Superior and Lake Michigan through at
least Friday morning. Multiple lake effect bands have already set up
off Lake Superior early this morning ans are streaming over the UP.
As winds increase today they will periodically impact RHI with MVFR
cigs and vsbys through through the afternoon. It is more uncertainty
how far south into central WI any showers progress so have limited
mention of precip at AUW and CWA to PROB30 groups.  For the Lake
Michigan shoreline, including MTW, north to north-northeast winds
will likely produce one or two dominate lake effect bands that may
cause periods of MVFR cigs and vsbys, mainly this afternoon through
this evening. For GRB and ATW have left precip mentions in a PROB30
group as there is some uncertainty if winds will take on enough of
an easterly component to snow flurries to drift that far in last.
Accumulations should be minimal at most TAF sites with the only
about a ~5% chance for greater than 1" at RHI and around a 10%
chance for 1" at MTW.

Northerly winds are already starting to increase early this morning.
THis trend will continue through the morning with peak gusts reaching
20-25kts by this afternoon. A few gusts up to 30kts are possible at
MTW as strong winds come off Lake Michigan. Winds will diminish some
tonight, however, gusts of 15-20kts may continue through much of the
TAF period.

&&

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

&&

$$

DISCUSSION.....Uhlmann
AVIATION.......GK

NWS GRB Office Area Forecast Discussion