188
FXUS63 KGRB 221132
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
632 AM CDT Thu Oct 22 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Dense fog late tonight into Thursday morning, locally dropping
  visibilities below 1/2 mile. More fog possible early Friday.

- Mild into the weekend with inland high temperatures warming into
  the middle 60s to lower 70s.

- Rain chances return Saturday night into Monday (20-40%).
  Additional chances for rain linger through much of next week.

- Cooler next week, with highs mainly in the 50s.

&&

.DISCUSSION...
Issued at 1113 PM CDT Wed Oct 21 2026

Fog trends through Friday morning...Cold front over northern WI
will stall, wash out over WI on Thursday. Winds behind the front
switch to NE which will bring lake moisture back into mix for the
fog. Later tonight, will see fog develop, mainly shallow/ground
type we saw early Wednesday morning. However, slug of stratus and
fog over Lake Superior is forecast to advect into far northeast WI
toward daybreak Thursday, spreading to west of the Fox Valley and
across Door County/lakeshore. Not sure how much fog occurs in the
Fox Valley on Thursday morning, but that will be something to
monitor. Dense fog is likely, but confidence is not there yet to
issue an advisory. High resolution guidance and blended guidance
suggests Marinette into Door County most favored. Given the onshore
sfc winds and weak flow aloft, patchy fog and stratus could linger
well into the afternoon for some of the area.

After a brief hiatus in the lower vsby later Thursday, east winds
and moisture off the lake and bay combined with nighttime cooling
should result in more fog Thursday night into early Friday, which
could be dense at times. Dense fog pattern eases up on Friday
night with increasing winds and warmer temps.

Dry Through Saturday Afternoon: Mid-level ridge stays locked in
through Saturday leading to mostly tranquil and dry weather across
the forecast area. Inland high temperatures will reach the upper
60s to lower 70s, while onshore lake breezes keep it cooler near
Lake Michigan.

Increased Rain Chances Saturday Night Through Monday: A northern
stream shortwave trough advancing across central Canada will push
an associated cold front across the Upper Midwest Saturday night
into Sunday. Moisture pooling along the slow-moving frontal
boundary will increase rain shower chances to 20 to 40 percent
across north-central and northeast Wisconsin Saturday night. Small
chances linger on Sunday, with a resurgence of scattered showers
later Sunday night through Monday. LREF higher than NBM regarding
extent of chances, but shows up to 70% chance of seeing 0.01 inch
and up to 50% chance of seeing 0.10 inch. So, still looking like a
higher POP/low QPF type of setup with frontal boundary nearby or
just to the south and right entrance of jet/frontogenesis enhancing
the rain chances. Deterministic models show more variability than
ensembles and NBM in location/timing of the steadiest rain, so
this will have to be sorted out over the coming days. Beyond Monday,
signal persists for a more unsettled weather pattern into the
middle of the week with at least small chances of showers as mid-
level flow becomes more zonal and active with multiple shortwave
troughs moving through.

Cooler Temperatures to start next week: Post-frontal cold air
advection will usher in a significantly cooler Canadian airmass
Monday through Tuesday, dropping daytime high temperatures into
the upper 40s to lower 50s area-wide. It is brief though as
temperatures show slight warming trend later next week. Nighttime
lows will fall back into the 30s.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 632 AM CDT Thu Oct 22 2026

Fog has been slower to develop this morning than previously, over
the past few hours areas of dense fog have developed over and along
the Bay of Green Bay. This fog will mainly impact GRB this morning
with IFR/LIFR vsbys expected through about 14Z with fog then lifting
to an IFR/MVFR status deck before clearing this afternoon. Given
current trends ATW and MTW may avoid the fog, however, have included
a brief TEMPO group at both sites through 14Z with IFR vsbys
possible. Across central and north-central WI expect mostly clear
skies through the TAF period. Another round of fog is possible
across east-central WI early Friday morning.

Winds will be light at less than 10 kts through the period.

&&

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

&&

$$

DISCUSSION.....JLA
AVIATION.......GK

NWS GRB Office Area Forecast Discussion