662
FXUS63 KGRB 031130
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 AM CDT Thu Sep 3 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- First round of thunderstorms will move across the area this
  morning into early this afternoon. Some of the storms could
  become severe with damaging winds and large hail along and
  south of Highway 29.

- There may be a lull or a break in the thunderstorm activity
  during the afternoon, another round of strong or severe
  thunderstorms is possible again late this afternoon and
  tonight.

- Above normal temperatures and periodic rain/storm chances will
  continue into the weekend.

&&

.DISCUSSION...
Issued at 215 AM CDT Thu Sep 3 2026

Another warm early September morning with temperatures in the 60s
to lower 70s. Patchy fog developed in some spots and will monitor
the lakeshore where some patchy dense fog may be possible on Lake
Michigan where recent upwelling has cooled off water
temperatures.

Complex forecast this morning dealing with potential for strong
or severe thunderstorms at times through late tonight. First
round of thunderstorms expected to move across the area this
morning into early this afternoon. Looking at two signals for
this to happen. Latest models indicated scattered thunderstorms
will develop between 08z and 11z across central into east-central
WI in response to a 40 knot/850 warm advection on a low level jet.
Also watching convection developing across southern Minnesota and
northern Iowa that will make its way eastward into our area later
this morning. Bufkit soundings at Green Bay indicated 40-50 knots
of 0-6 km shear, surface base CAPE of 1,000-1,500 J/Kg with most
unstable CAPE values around 2,000 J/KG. Some of the storms could
become strong or severe with damaging winds, large hail and
torrential rainfall this morning.

There will likely be a lull or break in the thunderstorm activity
this afternoon. With the best instability to our south, scattered
thunderstorms may redevelop during the peak heating of the day
across central into east-central WI closer to the best instability.
Some of these storms could become severe as well. The plot
thickens tonight with a complex of thunderstorms developing
across the Upper Midwest. The latest Canadian/ECMWF/NAM/GFS model
would suggest a complex of thunderstorms would work into the area
during the late evening and overnight hours. However, there are a
few meso models would suggest development would occur during the
evening closer to the better instability and then drop south into
southern WI.

There are periodic chances of thunderstorms while above normal
temperatures will continue Friday into early next week as the
summer time pattern continues.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 625 AM CDT Thu Sep 3 2026

First round of showers and storms will move across much of the
area this morning. The greatest risk for strong winds and large
hail will be along and south of Wausau to Kewaunee line.
Additional storms will develop south of this line by late
afternoon while a complex of storms will move its way
across the area later this evening and overnight. Besides
thunderstorms impacting aviation, CIGS may drop into the IFR
category in some spots late tonight into Friday morning along with
patchy fog. Any lingering rain should come to an end Friday
morning with improving CIGS and VSBYs during the day.

&&

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

&&

$$

DISCUSSION.....Eckberg
AVIATION.......Eckberg

NWS GRB Office Area Forecast Discussion