322
FXUS63 KGRB 030716
AFDGRB

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

Forecast discussion for routine morning forecast 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 06Z TAF Issuance
Issued at 1053 PM CDT Wed Sep 2 2026

A rather complex TAF period with uncertainty regarding fog, low
clouds and shower/storm chances overnight into Thursday. The
simple part is late this evening where VFR conditions will
prevail as mainly mid/high clouds drift across the region. The
light winds, clear skies will allow for some fog to form, but
guidance not very bullish on anything widespread or dense, with
the higher chances (under 30% for under 3 mile vsby) over eastern
WI. Have included mainly MVFR BR for now and will monitor fog
trends. Low clouds are also possible early Thursday morning, with
some guidance showing a 700-2000 ft deck, but again, not much
agreement to have much confidence this will occur.

Finally, the shower/storm threat is quite muddled, but latest
guidance is increasing the coverage of with elevated convection
possible as early as 07-09z across central and east-central WI,
with a larger area possible after 12-13z Thursday. Depending on
what occurs with those area, another round of showers and storms
may or may not occur Thursday afternoon and evening. The end
result will be plenty of TEMPO and PROB30 groups to account for
the more likely periods of storms, but adjustments will be needed
as the picture will hopefully become a little clearer. There
remains a low-end ~20% chance that a storm becomes strong to
severe with strong wind gusts and hail being the main impacts
along with heavy downpours. Wind will remain fairly light away
from any storm.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion