838
FXUS63 KGRB 032251
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
551 PM CDT Sat Oct 3 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Chance of showers (40 to 90%) at times through late tonight.
  Greatest chances of over 0.25 inch of rain far north-central WI.
  Otherwise, mainly dry through next week.

- Areas of frost across northern Wisconsin both Sunday and Monday
  nights. Greatest chance for a widespread frost/freeze event
  will be Sunday night.

&&

.DISCUSSION...
Issued at 101 PM CDT Sat Oct 3 2026

Rain chances through Sunday...Weak warm air advection has been main
trigger for isolated light showers seen so far today over WI.
Expect a few showers through late this afternoon especially
north-central on tail of wave crossing Lake Superior and just
ahead of weak elevated instability. Thunder risk does appear to
stay confined to far western WI. Better push for rain showers
moves through this evening as shortwave trough and stronger
forcing slide through. Decent agreement that north-central sees
the most rain by daybreak Sunday with over 0.25 inch, but mainly
less than 0.50 inch. Though chances have increased into south and
eastern areas as well late evening and overnight, the rain amounts
will be mostly less than 0.15 inch. Rain shifts east of area after
4a Sunday as weak cold front moves through. Northwest flow across
Lake Superior could squeeze a few sprinkles out over far north
from a shallow stratocu deck, but marginal over-water instability
and shallow moisture/low inversion height will keep main impact
to lingering clouds in the morning. By afternoon, skies should
become mostly sunny, even up north.

Frost/freeze potential...After a reprieve from frost/freeze issues
tonight due to the clouds/rain moving through, arrival of high
pressure ridge and clearing leads to another round of frost/freeze
Sunday night and again Monday night, then again later this week
over the north. For Sunday night, NBM showing similar footprint
to what occurred this morning for temps less than 36F, with a
40-80% chance of temperatures below 33 over the northern tier of
counties. GFS MOS guidance points to sub-freezing temps as well.
Monday night pretty similar, though with center of high shifting
east, greatest risk of temperatures below 33 is shunted toward
far northeast WI, with less signal over north-central WI. Expect
additional frost/freeze headlines to be issued for both nights.
Though not as pronounced yet, arrival of another high brings more
potential for frost/freeze over far north late this week as well.

Extended...Cold front comes through on Wednesday, but looks too
starved for moisture to produce any rain. Sharper northwest flow
aloft and stronger shortwave may drop across late this week, but
strongest lifts probably stays north resulting in LREF showing
less than 25% chance of seeing even a few hundredths. Maybe a bit
better shot of some rain beyond next weekend per LREF and AI
guidance, but overall as mid shift said, the longer we go without
significant rain, we could start to have increasing fire weather
concerns over the next several weeks due to current drought status
and increasing fine fuels as we experience repeated frost/freeze
conditions.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 546 PM CDT Sat Oct 3 2026

A cold front will bring a band of rain across northern Wisconsin
this evening into early Sunday morning, especially north of
Highway 10. The most notable change to the forecast was to add
wind shear this evening into early Sunday morning for all the
TAF sites 220-230 degrees at 35 to 40 knots. As the rain exits
the area, low clouds in the MVFR category will likely develop
across the north, impacting KRHI. Uncertainty exists if cloud
bases would be in the MVFR category at KAUW/KCWA/KGRB/KATW/KMTW
later tonight. Otherwise, gusty northwest winds can be
expected Sunday, especially until mid afternoon with some
locations gusting between 20 and 25 knots. Winds will quickly
subside by 00z Monday.

&&

.MARINE...
Issued at 101 PM CDT Sat Oct 3 2026

Increasing southerly winds into this evening will result in
conditions hazardous to small craft developing along the
nearshore waters of Lake Michigan into early this evening, and
lasting into Sunday morning. Southwest winds will gust to 25
knots, with waves building to 4 to 6 ft, highest near Death`s
Door and the lake side of Washington Island.

&&

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

&&

$$

DISCUSSION.....JLA
AVIATION.......Eckberg
MARINE.........JLA

NWS GRB Office Area Forecast Discussion