378
FXUS63 KGRB 091138
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
638 AM CDT Fri Oct 9 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Patchy frost is expected early this morning across north-
  central and far northeast Wisconsin as low temperatures fall
  into the mid-30s.

- Conditions will become hazardous to small craft from late
  tonight through Sunday as breezy southerly winds generate high
  waves.

- Unseasonably warm and windy conditions are expected this weekend
  with inland high temperatures into the upper 70s to middle 80s.

- A cold front traversing Wisconsin late Sunday night into Monday
  night will bring a 40-50% chance of light rain. Rain shower
  chances increase to 40 to 50% Wednesday into Thursday.

&&

.DISCUSSION...
Issued at 1030 PM CDT Thu Oct 8 2026

The current surface analysis shows high pressure stretching from
the northern Plains across the western Great Lakes, delivering
clear to partly cloudy skies and light winds across northern
Wisconsin. On the western flank of the ridge, a warm front is
advancing northward across the central Plains. High pressure will
bring quiet weather through Friday afternoon before warm
advection surges into the state. Unseasonably warm and breezy
conditions will dominate the region over the weekend before a cold
front arrives late Sunday night.

Patchy Frost Early Friday Morning: High pressure centered
over Wisconsin tonight will create favorable radiational cooling
conditions beneath light winds and partial sky clearing. Overnight
minimum temperatures will drop into the mid to upper 30s across
north-central and far northeast Wisconsin, including Land O Lakes,
Rhinelander, and Crandon. NBM statistical guidance shows a 50 to
80 percent probability of temperatures falling below 37 degrees,
supporting patchy frost development. Rapid diurnal solar heating
after 13Z Friday will burn off patchy frost with daytime highs
recovering into the upper 60s under mostly sunny skies.

Unseasonable Weekend Heat And Marine Hazards: As surface high
pressure shifts to the East Coast, an intense upper-level ridge
will build across the western Great Lakes, increasing warm
advection this weekend. Inland daytime high temperatures on
Saturday and Sunday will climb into the upper 70s to mid-80s
across Wisconsin, putting daily record high values in jeopardy.
Tightening regional pressure gradients will drive gusty southerly
winds of 25 to 35 mph, while NBM probabilistic guidance shows a 60
to 90 percent probability of wind gusts exceeding 30 mph.

Early Week Cold Front Shower Probabilities: A cold front
associated with a northern stream shortwave will cross Wisconsin
late Sunday night into Monday, bringing rain shower chances.
Ingestion of Gulf moisture remains limited, keeping 24-hour
precipitation probabilities between 30 and 50 percent across
central and northern Wisconsin. NBM probabilistic guidance
indicates only a 15 to 25 percent probability of 24-hour liquid
accumulations exceeding 0.25 inches, reflecting a light rainfall
event. Post-frontal cold air advection Monday night will drop
daytime high temperatures back into the upper 50s and lower 60s
for early next week.

Midweek System Rain Shower Potential: Another mid-level shortwave
trough and associated surface wave will traverse the Upper
Midwest Wednesday into Thursday, increasing precipitation chances
across the forecast area once again. Dynamic forcing and renewed
moisture transport will support a 40 to 50 percent chance of rain
showers area-wide. Elevated instability up to 400 J/kg may allow
for isolated thunderstorm activity, though severe weather
chances remain near zero. NBM ensemble guidance exhibits tight
temperature spreads with daytime highs staying held in the upper
50s and lower 60s under mostly cloudy skies. A significant cooling
trend will follow this system for the end of the week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 636 AM CDT Fri Oct 9 2026

VFR conditions are expected through this TAF period. An area of
mid and high clouds was observed over central and east-central WI
this morning. While the mid clouds are expected to dissipate by
mid-morning, the high clouds will stick around at times throughout
the day. Ahead of an approaching warm front, a surge of low
clouds will move across the area from the southwest to northeast
after 23z Fri with cloud bases around 4000-5000 ft AGL. These low
clouds will exit the region towards the end of this TAF period.

Light and variable winds are expected this morning before winds
shift to the southeast at 5-10 kts this afternoon. A brief period
of LLWS is possible after 05z Sat as south winds of 35-40 kts are
anticipated above the southeast surface winds.

&&

.MARINE...
Issued at 1030 PM CDT Thu Oct 8 2026

Southerly winds are forecast to increase Friday night and remain
gusty through the weekend. Waves are expected to build to 4-8 ft
on Lake Michigan from Friday night through Saturday night. South
winds to 30 kts are possible on Saturday and Saturday night. Small
craft advisories will be required from Friday night through
Sunday.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion