635
FXUS63 KGRB 111127
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
627 AM CDT Fri Sep 11 2026

Updated aviation portion for 12Z 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 12Z TAF Issuance
Issued at 627 AM CDT Fri Sep 11 2026

VFR conditions are expected today ahead of a chance for showers and
storms tonight. This morning some SCT to BKN cigs bases around 9kft
are drifting across northern WI. These cigs should scattered out by
afternoon leaving mostly clear skies into this evening. High clouds
ahead of tonights chance for showers and storms will start to move
over the region late this evening with cloud bases around 12kft.
CAMs show a narrow line of showers/storms then moving across the
region between 07-12Z Sat. Highest confidence in precipitation is at
RHI as CAMs generally show showers becoming more isolated with
southward and eastward extent. A rumbles of thunder are possible
across northern WI, but confidence in thunder is too low to include
in at RHI with this TAF issuance.

Winds will become south-southwesterly today, gusting to 15-20 knots
this afternoon and evening, with the highest gusts in north-central
WI and over Door County. A few gusts near 25 kts are also possible
in these areas.

&&

.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 from 3 PM CDT this afternoon through
Saturday afternoon for WIZ022.

Beach Hazards Statement from 3 PM CDT this afternoon through
Saturday morning for WIZ040-050.
&&

$$

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

NWS GRB Office Area Forecast Discussion