064
FXUS63 KGRB 241140
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
640 AM CDT Sun Aug 24 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- First glimpse of early fall expected through early next week
  with cooler temperatures. Scattered showers will be possible at
  times, especially today.

- Some waterspouts are possible today into Monday across the bay
  of Green Bay and Lake Michigan. The greatest potential occurs
  from late morning through early evening today.

- Patchy frost possible in north-central Wisconsin late Monday
  night and late Tuesday night.

&&

.DISCUSSION...
Issued at 308 AM CDT Sun Aug 24 2025

An upper low over James Bay will slowly drift southeast through
Quebec through early next week. Numerous short-waves will rotate
through the western Great Lakes through Tuesday, bringing
periodic light shower chances through at tonight. The strongest
wave will move through today, when shower chances will exist
regionwide, with a few thunderstorms possible. The showers will
be concentrated over far NC WI and northern Door County,
especially through tonight, when cold northwest flow off the
Great Lakes will produce lake-effect rain showers. Despite the
arrival of additional shortwaves, the models don`t show much
precipitation past tonight, likely due to the arrival of much
drier air (PWATs around 0.5 inch).

The pattern also favors waterspout development on the bay and
Lake Michigan, especially today into Monday. The best combination
of lake-induced instability (Lake-850 mb delta-T`s of 16-18 C)
and convective cloud depth (10k-20k feet) occurs from the late
morning through the early evening today.

Dry conditions will persist through at least Wednesday; however,
a back door cold front will sag south through the area late
Wednesday night through Thursday and bring a small chance of
light showers. Although the NBM has finally latched onto this
feature in some capacity, raised POPs during this period to
reflect better chances of showers than the NBM would suggest by a
few percentage points. Mainly dry weather returns late in the
week.

Much cooler temperatures are expected for the rest of the weekend
into early next week, with highs only reaching the upper 50s and
60s through Monday. Depending on cloud cover, there is potential
for patchy frost in the Northwoods late Monday night and late
Tuesday night, as low temperatures fall into the 30s. Temperatures
will slowly moderate back into the 70s by the middle to late part
of the week, but still be a few degrees below normal for this
time of year.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 640 AM CDT Sun Aug 24 2025

The latest RAP analysis and satellite/radar imagery show cool,
cyclonic flow encompassing the western Great Lakes late this
morning. A deck of MVFR stratus clouds has made it over north-
central and central Wisconsin and should continue moving southeast
before eventually lifting to VFR later this morning and into the
early afternoon for most locations south of north-central
Wisconsin. Scattered light shower activity is forecast to become
more widespread after 15z and have kept a tempo group at all TAF
sites for the afternoon. Skies will then clear out from southwest
to northeast tonight as drier air moves into the region.

Northwest winds will pick up this morning and become breezy with
gusts to 20 kts before subsiding this evening.

&&

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

&&

$$

DISCUSSION.....Kurimski
AVIATION.......Kurimski