838
FXUS63 KGRB 020342
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1042 PM CDT Wed Oct 1 2025

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Warming trend through the weekend, with daily high temperatures
  peaking Friday and Saturday in the mid 80s. Record or near
  record highs are expected.

- Hazardous conditions for small craft on Lake Michigan late
  tonight through Thursday afternoon. Another round of strong
  winds and higher waves this weekend. Very breezy conditions on
  land Saturday and especially on Sunday.

- Most locations stay dry until Sunday night with arrival of
  stronger cold front. Chance for isolated to scattered showers
  (20-30%) lasts through Monday night, but average rainfall
  amounts will be less than 0.25 inch.

&&

.DISCUSSION...
Issued at 343 PM CDT Wed Oct 1 2025

The very quiet weather of late September will continue into early
October as high pressure will continue its reign over the Great
Lakes. Very few rain/storm chances, with only a weakening front
clipping the far north late Thursday into Friday, and a stronger
front Sunday night into Monday. But moisture will be lacking, so
any threat for significant precip is low. Temps and increasing
winds (bringing marine and possible fire weather concerns) will be
the bigger story as we will have 3 days of potential record
breaking warmth.

Temps & Potential Fire Wx Concerns: Southerly flow will usher in
well above normal temps for the rest of the week and into
Saturday. Strong signals for record or near record warmth, peaking
Friday into Saturday, where many records are likely to fall. NBM
25th to 75th percentile spread remains very low, with highs in the
mid 80s for much of central WI and low 80s over north-central WI.
ECMWF Extreme Forecast Index of 0.8-0.9 also signaling a very
unusual (record setting) event is likely. Some upper 80s will be
possible in some of the hot spots if we can realize 850mb temps of
18C. Very warm conditions are expected Friday and Saturday
nights as well, with lows mainly in the 60s. Record high mins
likely to fall. The very warm temps, low RH`s in the 30/40s, more
and more leaves falling off the trees, and recent dry conditions
will combine with gusty south to southwest winds to increase fire
weather concerns this weekend. Fuels are a question mark, along
with just how dry/windy it will be, but the increased fire weather
threat will need to be watched. The strong cold front will usher
in much cooler air into the region Monday into Tuesday, with highs
falling back into the 50s and 60s.

Winds & Marine Hazards: A brief period of small craft conditions
are expected south of Sturgeon Bay on Lake Michigan tonight into
Thursday as persistent south winds builds waves to around 4 ft. No
changes to the Small Craft Advisory. And as a reminder, no Beach
Hazards Statements will be issued as the Beach Hazards season
ended on 9/30. Another period of strong, persistent
south/southwest winds is forecast for Saturday into early Monday
as low pressure passes to our west. Gusts to 30 kts are looking
likely. Waves are forecast to build to 4-8 ft on Lake Michigan and
to 2-4 ft on the bay. On land, breezy conditions are expected
this weekend with southerly winds gusting 20-30 mph on Saturday
and south/southwest winds gusting to 25-35 mph (possibly 40 mph)
on Sunday as winds peak out around 50 kts at 5000 ft and mixing
increases to 4000-5000 ft.

Shower/Storm Chances: A weak front will clip the U.P. and
northern WI late Thursday into Friday. Moisture will be lacking
and short-lived, so an shower threat looks to be over the far
north and relatively brief. Have continued the dry forecast, but
some low-end PoPs may be needed for the north. The next chance
for rain arrives as a stronger front moves across the region late
Sunday into Monday. Deep moisture will again be an issue, likely
keep the precip on the lighter side and not very widespread. If we
don`t get any noteworthy rain with these two systems, drought
conditions will worsen and fire weather concerns will continue to
rise.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1032 PM CDT Wed Oct 1 2025

Have increased the potential for fog/low stratus in the forecast
overnight into early Thursday, especially in the SE wind upslope
region of far NE WI and near Lake Michigan. Patchy fog has already
been observed near the lake, and dew point depressions were
getting low in parts of NE WI. For now, plan to only include fog
and low stratus in the MTW and GRB TAFs, but there is small
chance that RHI could see some too.

Otherwise, looking at BKN high clouds overnight into early
Thursday, then FEW-SCT cumulus clouds developing in the late
morning and afternoon. Winds will be light from the southeast
tonight, then pick up a bit from the SE-S by Thursday afternoon.
Guidance is suggesting potential for some low stratus over parts
of northern WI late tomorrow night, though that is beyond this
TAF period.

&&

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

&&

$$

DISCUSSION.....Bersch
AVIATION.......Kieckbusch