NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 111743
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1243 PM CDT Fri Sep 11 2026

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Chances for thunderstorms return tonight into Saturday morning.
  The severe weather threat is low.

- A round of heavy rain and thunderstorms is possible Monday into
  Tuesday. However, predictability of any severe storms is low.

- Gusty south-southwest winds will generate high waves along Lake
  Michigan this afternoon through Saturday morning, causing
  hazardous conditions to small craft and dangerous swimming
  conditions at Lake Michigan beaches.

&&

.DISCUSSION...
Issued at 150 AM CDT Fri Sep 11 2026

Shower and Storm Chances Return Tonight: With weak high pressure
lingering over the region today expected dry conditions through the
daylight hours. This evening a short-wave impulse and surface cold
front will set off a cluster of thunderstorms across Minnesota where
an increasingly unstable airmass will be in place. As these
storms track east towards central and north-central WI this
evening the expectation is they will weaken due to diminishing
instability and weaker forcing. Areal extent of showers and
storms is also expected to become more isolated overnight with
eastward extend. May see a brief window for storms to re-intensify
Saturday morning as some CAMs show a narrow corridor of
instability developing east of I-41. However, forcing will be
limited during this period so not confident storms will even
develop. Weak high pressure is then progged to move in returning
dry conditions for the remainder of the weekend.

Heavy Rain and Storms Early Next Week: Global ensembles are in
decent agreement that a strong synoptic low-pressure system will
bring a widespread soaking rain to the region late Sunday through
Monday.  A strong mass response ahead of the surface low will
increase PWATs to 1.7-1.8" which is above the 95th percentile of
climatology. With the abundant moisture and strong forcing NBM probs
are showing a 30-60% chance for greater than 2" of rain Monday, with
the highest chances across central WI. There is also a low end
chance for stronger embedded thunderstorms, however, the strongest
instability is expected to remain south and west of the region which
should limit the severe potential.

Rest of the forecast: There continues to be low chances (20-30%)
for precipitation during the middle of next week as zonal flow
sets up across the Great Lakes. This period could just as easily
be dry as it could be light showers as the models are uncertain
how close a surface boundary will be to the region. If the high
wins out we stay dry, if the boundary is further north we could
see some showers at times. The one thing that seems certain is
that we will be noticeably cooler with highs only in the 60s.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1243 PM CDT Fri Sep 11 2026

VFR conditions will continue into early this evening with a few
mid/high clouds and a few puffs of daytime cu (especially near
Lake Michigan). CAMs continue to show a narrow line of showers/
storms moving across the region between 06-12Z Sat. Highest
confidence in precip and lower ceilings (mainly MVFR) is at RHI as
CAMs generally show showers becoming more isolated with southward
and eastward extent, with the activity likely weakening before
getting to GRB/ATW/MTW with only a sprinkle possible. A rumbles of
thunder are possible across northern WI, but confidence in
thunder is too low to include in at RHI. An area of MVFR clouds is
expected behind the showers. As a front exits the area Saturday
morning, a stray shower will be possible over far eastern WI.

South-southwesterly winds will continue this afternoon, gusting
to 15-20 through around sunset, with the highest gusts in north-
central WI and over Door County. A few gusts near 25 kts are also
possible. Winds will decrease a little after sunset and into
tonight, then shift to the west-northwest Saturday morning, with
gusts to 20 kts. Southwest/west LLWS is expected overnight as
winds around 2000 ft increase to 40-45 kts.

&&

.MARINE...
Issued at 150 AM CDT Fri Sep 11 2026

Small Craft Advisory and Beach Hazards Statement are in effect
for this afternoon through Saturday morning for gusty south winds
to 30 kts and waves 3-6 ft. Another period of breezy southeast
winds will lead to increasing waves next Monday into Tuesday.
Addtioanl Small Craft Advisory and Beach Hazard Statements may be
needed.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement through Saturday afternoon for WIZ022.

Beach Hazards Statement through Saturday morning for WIZ040-050.
&&

$$

DISCUSSION.....GK
AVIATION.......Bersch
MARINE.........GK