504
FXUS63 KGRB 151133
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
633 AM CDT Thu Oct 15 2026

Updated aviation portion for 12Z TAF issuance

.UPDATE...
Issued at 225 AM CDT Thu Oct 15 2026

Upgraded the Gale Watch to a Gale Warning for the bay and
our nearshore waters of Lake Michigan from 8 am to 9 pm Friday.
The Gale Warning was started a few hours early to cover the
ramp up of hazardous small craft due to increasing winds and
waves until gale force gust arrive late Friday morning and
continue through the afternoon.

&&

.KEY MESSAGES...

- Widespread rain arrives Thursday afternoon, and will continue at
  times through Friday. Expect most areas to see between 0.5 and
  1" of total rainfall.

- Northwest winds increase on Friday, with gusts between 35 and 45
  mph possible. Gale force gusts expected across marine zones.

- A widespread frost/freeze event is expected Friday night into early
  Saturday morning.

- A warming trend and breezy southwest winds will bring daytime high
  temperatures back into the 60s late this weekend, with minimal
  rain chances through mid-week.

&&

.DISCUSSION...
Issued at 1000 PM CDT Wed Oct 14 2026

Rain chances Thursday/Friday... Biggest change from previous
forecast cycles centers around a noticeable jump in QPF amounts
Thursday through Friday as models hone in on timing/evolution of
the upper pattern. Signs still point toward phasing of northern
and southern stream lows over the western Great Lakes Thursday
night as a deepening surface low ejects from the central Plains.
Jet energy ramps up during this time as moisture plume (near 99th
percentile PWATs) interacts with mid-level FGEN in proximity to
low pressure over southern Wisconsin. As such, probabilities for
receiving one inch of QPF now stand at a widespread 30 to 60%.
Thus expecting a soaking rainfall across most of northeast
Wisconsin, which will be beneficial to areas across the north
that have been in an extended period of drought. Stratiform rain
then becomes more scattered in coverage on Friday, though wrap
around moisture should keep at least light rain around for most of
the day.

Temperatures... Following a decent stretch of seasonable
weather, cold FROPA and intrusion of arctic high will bring a
brief spell of well below normal temperatures from the Plains to
the Midwest on Friday. 850 mb temperatures plunge to around 2 to
5C below zero, which will translate to high temperatures
reading in the mid 40s across the north to the mid 50s in the Fox
Valley. Overnight lows will then fall into the mid 20s to low 30s
inland of Lake Michigan, pointing toward a high confidence setup
for frost/freeze under clearing skies and light winds. If trends
hold, expect most areas to see a hard freeze that would
effectively put an end to the growing season. Expect headlines to
be forthcoming in the next day or so. Return flow then quickly
sets up over the weekend, resulting in high temperatures
rebounding into the 60s.

Extended... High pressure looks to be the main driver of the
synoptic pattern through at least the middle of next week, with
no organized systems on the horizon. More active pattern looks to
set up beyond then as upper flow re-amplifies, though details are
few this far out.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 626 AM CDT Thu Oct 15 2026

CIGS will continue to fall into the IFR category later this
morning into the afternoon as rain and drizzle overspread
the area today. The poor flying conditions continue this evening
with rain and fog, then conditions gradually improving late
tonight into Friday morning. The other big story will be strong
northerly winds that may gust to 30 to 40 knots on Friday that may
impact departures/arrivals. The wind should quickly subside
Friday evening.

&&

.MARINE...
Issued at 1000 PM CDT Wed Oct 14 2026

Upgraded the Gale Watch to a Gale Warning for the bay and
our nearshore waters of Lake Michigan from 8 am to 9 pm Friday.
The Gale Warning was started a few hours early to cover the
ramp up of hazardous small craft due to increasing winds and
waves until gale force gust arrive late Friday morning and
continue through the afternoon.

From the previous discussion:

Gradient winds on the back edge of the departing surface low ramp
up Thursday night into Friday morning, putting us solidly within
northwest flow and CAA regime. Deep daytime mixing will tap into
45 to 50 knot winds at 850 mb Friday afternoon, which will
result in a brief window for gale force gusts over all marine
zones through Friday evening. NBM probabilistic guidance continues
to show a healthy signal (60 to 90%) for gusts exceeding 38 mph,
highest along the Lake Michigan nearshore waters south of
Kewaunee. Waves build 6 to 9 ft on the Lake and 3 to 6 ft on the
Bay during this time, subsiding Friday night as winds shift to
more westerly and the pressure gradient eases up. Gale Watches
remain in effect.

&&

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

&&

$$

UPDATE.........Eckberg
DISCUSSION.....Goodin
AVIATION.......Eckberg
MARINE.........Goodin/Eckberg

NWS GRB Office Area Forecast Discussion