405
FXUS63 KGRB 072330
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 PM CDT Mon Sep 7 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Rain and storms chances (60-80%) return late tonight through
  late Tuesday night. A few strong storms are possible Tuesday
  morning and again Tuesday evening and night.

- Gusty winds and high waves Tuesday through Wednesday will result
  in hazardous conditions to small craft. There will also be an
  increased risk of rip currents at Lake Michigan beaches Tuesday
  into Wednesday morning.

- Temperatures at or above normal continue into the weekend.

&&

.DISCUSSION...
Issued at 325 PM CDT Mon Sep 7 2026

Precip/Storm Potential Tonight through Tuesday Night...The
prevailing high pressure system will gradually depart tonight and
allow return flow to increase over the area ahead of an approaching
shortwave/trough and cold front. Ahead of the front, a southwesterly
LLJ (35-45 kts) and increasing WAA will aid in rain showers
developing over eastern MN and western WI late tonight. These
showers will move into central and north-central WI by early Tuesday
morning and gradually move east/southeastward across the remainder
of the forecast area through the rest of the morning. Cannot rule
out the potential of some elevated thunderstorms producing a few
strong storms capable of strong wind gusts or hail given 400-800
J/kg of MUCAPE and effective shear around 30 kts. This shower/storm
activity will lessen in coverage by Tuesday afternoon as the
LLJ/instability decreases, but will not end. Some CAMs show an
uptick in the shower/storm activity during the evening and night
with the arrival of the cold front, but there is plenty of
uncertainty in this development. If these storms develop, a few
storms could be strong/severe with 400-800 J/kg of MUCAPE (including
some 100-200 J/kg of SBCAPE) and 30-40 kts of deep-layer shear.
There will also be an increased risk of heavy rainfall/downpours
given PWATs will be around 1.75-2.00 inches throughout the period.
In addition to the precip/storm potential, breezy south winds are
expected on Tuesday gusting to 20-25 mph.

Rest of the Forecast...Dry conditions are forecast for Wednesday
through much of Friday as high pressure prevails. However, following
the cold frontal passage Tuesday night, a tight pressure gradient
will develop on Wednesday leading to gusty westerly winds of 30-35
mph. The next chance of showers and storms arrives Friday night into
Saturday with a cold frontal passage. Confidence is low on timing
and placement of convection. Aside from near normal temperatures on
Thursday, but temperatures will remain above normal.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 600 PM CDT Mon Sep 7 2026

Main impacts to aviation during this TAF cycle will center around
rain/storm chances late tonight through Tuesday. Mid and high
clouds will spread over the region during this time, eventually
thickening and lowering to MVFR near RHI by late Tuesday morning.
SHRA should arrive to the central and north-central sites between
06 and 12Z Tuesday, becoming more scattered in coverage by the
time they reach the east-central sites later in the morning. Have
included PROB30 groups for rain arrival at RHI, AUW, and CWA, and
TEMPO groups for heavier rain with reduced vsbys. Limited the
east-central sites to PROB30 mentions for the time being. Thunder
will be possible at times, though confidence in timing/occurrence
was too low to warrant inclusion in this TAF issuance.

Southerly winds ramp up ahead of an approaching cold front
Tuesday afternoon. Prevailing winds will be around 10 to 15 knots,
with gusts to 20 knots at all sites. Locally higher gusts may be
possible near MTW.

&&

.MARINE...
Issued at 325 PM CDT Mon Sep 7 2026

Southerly winds will increase on Tuesday and result in high
waves on the nearshore waters of Lake Michigan and northern Green
Bay. A lull in the winds is expected early Wednesday morning, before
increasing again and veering west late Wednesday morning. Conditions
will be hazardous to small craft during these times. There will also
be an increased risk of rip currents mainly Tuesday into Wednesday
morning, until winds turn offshore. Small Craft Advisories and Beach
Hazards Statements remain in effect, but delayed the start time to 1
PM due to a delay in the building waves. Another Small Craft
Advisory will be needed for Wednesday afternoon/evening, once the
westerly winds increase.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from Tuesday afternoon through Wednesday
morning for WIZ022-040-050.
&&

$$

DISCUSSION.....Kruk
AVIATION.......Goodin
MARINE.........Kruk