855
FXUS63 KGRB 212339
AFDGRB

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

Updated aviation portion for 00Z TAF 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 00Z TAF Issuance
Issued at 638 PM CDT Mon Sep 21 2026

VFR conditions are expected for most of the TAF period, with a
period of high-end MVFR ceilings possible overnight into Tuesday
morning. Light rain showers and sprinkles have been steadily
advancing toward the area this afternoon and look to push into
portions of central and east-central WI. Have not included as no
aviation impacts are expected and the dry northeast flow should
slowly eat away at its advancement and limit what makes it to the
ground. Otherwise, high clouds over 15,000 ft will continue to
spread across the region at times.

East or northeast winds are expected through the TAF period,
gusting to ~15 kts, locally higher near the bay/Lake Michigan.

&&

.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.......Bersch
MARINE.........GK