820
FXUS63 KGRB 311141
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
641 AM CDT Sun Aug 31 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- No hazardous weather expected through Tuesday, with areas of fog
tonight the only minor impactful weather.

- Increasingly likely shower and thunderstorm chances (60% to 80%)
Wednesday.

- Record to near-record cold high temperatures becoming increasingly
likely for the back end of next week.

&&

.DISCUSSION...
Issued at 334 AM CDT Sun Aug 31 2025

Today through Tuesday:
Overall, fairly persistent and quiet weather is expected to
continue across our forecast area today through Tuesday. High
temperatures will be in the mid to upper 70s today and tomorrow...
which is near normal for this time of year.

We have around a 20% chance for a few showers in Vilas far northern
Wisconsin this afternoon. The challenge will be an abundance of dry
air for any precipitation to overcome. So virga to a few brief (~15
minutes or less) periods of showers appear to be the main highlights
for today. Interestingly, in sounding analysis, one has to go up to
500mb to find winds of over 10 kts. Therefore winds are expected to
be light not only across northern Wisconsin, but across our entire
area today.

With the light wind and mainly clear skies, areas of radiational fog
are expected to develop tonight. As of now, it appears the fog will
not be widespread enough to warrant any form of a Dense Fog
Advisory, but we will monitor. After sunrise, the fog will lift and
not yield any additional impacts.

Wednesday shower and thunderstorms:
Confidence is increasing (60% to 80% chance) for widespread
showers and thunderstorms associated with a cold front that models
are pushing across Wisconsin from northwest to southeast on
Wednesday. Of note, is that ensemble model trends are to slow the
progression of this feature. In previous iterations, model
consensus was bringing this boundary across our area late
Tuesday/Tuesday night. Most recent trends have been to delay this
to Wednesday morning/Wednesday afternoon.

As of now, severe weather is not expected with this system. However,
thunder chances are up to 40%, so lightning will be the biggest
impact. Based on wind speeds aloft, there could also be wind gusts
upwards of 30 to 35 mph. Additionally, heavy rainfall parameters are
stacking up to look nothing like they did with the moderate/heavy
rainfall events across the area from late July-mid August. Ensemble
models generally show less than a 15% chance of 1" of total
rainfall... so an 85% chance of less than 1" of rain.

Record to near-record cold temperatures behind this system:
For the past few days, long-range models have had a notably
potent blast of cold air making it into Wisconsin. In fact, this
scenario plays out much like a cold, dreary November event, where
it is cloudy, cold and breezy for several consecutive days. In the
Green Bay area, the record cold high temperature for a September
4 is 61 degrees, and for September 5, the record cold high is 60
degrees. As of now, there is a very, very plausible chance that
one or both of those records will be broken this year. Record low
temperatures are in the mid to upper 30s, and with the expected
cloud cover preventing completely pure radiational cooling, we may
not quite be able to break those records. Below normal
temperatures will likely continue through next weekend.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 639 AM CDT Sun Aug 31 2025

Light winds and mostly clear skies will prevail today, with a few
light showers possible in northern WI later this afternoon.

For tonight, once again, conditions are favorable for areas of
fog to develop. Kept visibility at MVFR or above at all sites,
except for KCWA. Incoming shifts today will be able to refine with
more precision.



&&

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

&&

$$

DISCUSSION.....Kotenberg
AVIATION.......Kotenberg

NWS GRB Office Area Forecast Discussion