851
FXUS63 KGRB 211931
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
231 PM CDT Mon Sep 21 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Hazardous boating and swimming conditions are expected on the
  Bay and Lake through Tuesday afternoon.

- Patchy areas of frost are possible early Tuesday morning across
  north-central WI. Additional periods of frost are possible
  through the week.

- A quieter and drier weather pattern will settle into the region
  for the next week.

&&

.DISCUSSION...
Issued at 231 PM CDT Mon Sep 21 2026

Minimally impactful weather is forecast through this weekend. For the
rest of today and tonight an upper-level low will move across
southern WI bring and increase in cloud cover to the region. An arc
of light showers has developed along the WI/MN border and will
slowly drift east through the evening, however, with dry mid-level
air in place, don`t expect more than a sprinkle to reach central WI
for before the precip dries away. While cloud cover tonight will
keep temperatures from bottoming out the presence of a cooler air
mass will allow lows to reach the low to middle 30s across north-
central WI which may result in patchy areas of frost in protected
and low laying areas. A similar set up is expected Tuesday night,
however, lows be a few degrees warmer as winds become more easterly.

With a Hudson Bay high expected to remain entrenched through next
weekend any weak short-waves moving towards the region will struggle
to produce any measurable rainfall. The next chance for more
widespread rain does not look to come until this high starts to
break down and a long wave trough moves passes across the region
early next week.

Temperatures this week will gradually trend warmer each day with
highs climbing back into the upper 60s to low 70s by the weekend.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1208 PM CDT Mon Sep 21 2026

Primarily VFR conditions are anticipated across the region through
the TAF period with brief periods of MVFR cigs possible this
afternoon. Northeast winds streaming in over the western Great
Lakes have allowed SCT to BKN fair weather cu bases around 2.5 to
3.5 kft to develop. Expect these clouds to gradually rise and
scatter out through this afternoon. Addtioanl high cirrus clouds,
based around 12 to 15 kft will overspread the region this afternoon
as a low pressure system passes south of the region. These high
based cigs will linger over the region tonight and through much of
Tuesday.

East or northeast winds are expected through tonight with gusts up
to 25 kts. Overnight winds will decrease with another uptick in
easterly winds Tuesday morning with gusts reaching 15-20kts.

&&

.MARINE...
Issued at 231 PM CDT Mon Sep 21 2026

The primary immediate weather hazard involves elevated winds and
high waves on the Bay and Lake. The pressure gradient between the
robust high pressure over northern Ontario and the advancing low
pressure to our west is producing onshore winds to 20 kts and wave
heights to 6 feet on Lake Michigan, and 3 to 4 feet on the Bay of
Green Bay this afternoon.

The gusty northeast winds will veer to the east on Tuesday and
remain gusty in the 20-25 kt range. As a result, Small Craft
Advisories and a Beach Hazards Statement look to remain on track.
Winds and waves might subside enough for an early cancellation on
the Bay late tonight or Tuesday, but conditions will undoubtedly
remain choppy with gusts to 20 kts. Therefore no changes planned to
the current marine headlines at this time. Winds and waves will
gradually subside late Tuesday into Wednesday as the pressure
gradient begins to relax.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from midnight tonight to 7 AM CDT Tuesday for
WIZ005-010>012-018.

Beach Hazards Statement through Tuesday evening for WIZ022-040-
050.
&&

$$

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