894
FXUS63 KGRB 071155
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
655 AM CDT Wed Oct 7 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Gusty west winds to 30 to 35 mph and low afternoon relative
  humidity will elevate fire weather concerns this afternoon
  across north-central and far northeast Wisconsin.

- Patchy frost will be possible over far northern Wisconsin early
  Friday morning with low temperatures in the mid 30s.

- Unseasonably warm and windy conditions arrive Saturday and
  Sunday with inland high temperatures into the upper 70s to lower
  80s.

&&

.DISCUSSION...
Issued at 1030 PM CDT Tue Oct 6 2026

The current surface analysis shows a prefrontal trough crossing
northern Wisconsin ahead of a cold front positioned over northern
Minnesota. Upper-air analysis displays broad mid-level troughing
over Ontario and Quebec, while an expansive surface high pressure
ridge builds across the Northern Plains. The cold front will pass
through dry tonight, shifting surface winds to the west by
Wednesday morning.

Gusty Winds And Fire Weather Wednesday: Deep boundary layer
mixing up to 750-700mb behind the cold front will drive minimum
relative humidity values down to 27 to 35 percent Wednesday
afternoon across Marinette, Florence, and Forest counties, where
there is a moderate fire danger. Modestly tight surface pressure
gradients will combine with momentum transfer aloft to yield gusty
west winds in these areas. NBM probabilistic guidance indicates a
60 to 80% chance of wind gusts exceeding 30 mph across the
northwoods. Relative humidity values will rapidly recover above
85 percent Wednesday evening as surface winds subside beneath
building high pressure.

Thursday Night Patchy Frost Potential: Canadian surface high
pressure building over the western Great Lakes Thursday night will
create favorable radiational cooling conditions beneath
decoupling winds and clear skies. Overnight minimum temperatures
will drop into the mid to upper 30s across north-central and far
northeast Wisconsin, including Rhinelander, Land O Lakes, and
Crandon. NBM temperature percentiles show a 30 to 50 percent
probability of low temperatures falling to 37 degrees or colder
in sandy soil areas, supporting patchy frost formation late
Thursday night. Rapid diurnal warming after sunrise Friday will
quickly burn off any patchy frost with daytime highs recovering
into the upper 60s.

Weekend Unseasonable Warmth And Strong Winds: Strong warm
advection and return southerly flow will surge across Wisconsin
Friday night into the weekend as high pressure shifts to the East
Coast. Inland maximum temperatures Saturday and Sunday will likely reach
the upper 70s to lower 80s, approaching daily record highs at some
locations. Tightening regional pressure gradients will produce
strong southerly wind gusts on Saturday, with NBM guidance showing
a 30 to 50% probability of gusts exceeding 35 mph area- wide.
High confidence exists in these unseasonably warm temperatures as
NBM 25th to 75th percentile spreads remain narrow at 2 to 4
degrees F across most of the area.

An advancing upper- level trough and associated surface cold
front will cross Wisconsin Sunday night into Monday, bringing
returning rain shower chances. Limited moisture transport ahead of
the boundary will restrict precipitation coverage, keeping
24-hour rainfall probabilities between 30 and 50 percent across
north-central and northeast Wisconsin. NBM probabilistic guidance
indicates a 15-30 percent probability of 24-hour rainfall
exceeding 0.50 inches, with expected liquid accumulations
remaining around 0.25 inches. Post-frontal cold advection Monday
night into Tuesday will drop daytime highs back into the upper 50s
and lower 60s for early next week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 654 AM CDT Wed Oct 7 2026

VFR conditions are expected through this TAF period with mid and
high clouds occurring at times. The main story will be the
increasing west to northwest winds this afternoon. The highest
gusts are expected at RHI/AUW/CWA/GRB/ATW, gusting to 25-30 kts.
Gusts up to 25 kts are expected at MTW. Gusts will subside by
00-02z Thu.

&&

.MARINE...
Issued at 1030 PM CDT Tue Oct 6 2026

Gusty south winds are subsiding, but waves on Lake Michigan will
likely take until early Wednesday morning before falling below
Small Craft Advisory criteria. Have ended the Small Craft Advisory
on the Bay but waves of 4 ft off Kewaunee to 10 ft on the northern
Lake Michigan buoy will take longer to diminish.

Gusty west winds to 25 kts are expected to develop on Wednesday
afternoon, which may require a Small Craft Advisory.

&&

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

&&

$$

DISCUSSION.....MPC
AVIATION.......Kruk
MARINE.........MPC

NWS GRB Office Area Forecast Discussion