Bryant, Wisconsin Weather Forecast Discussion

439
FXUS63 KGRB 221735
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
1235 PM CDT Mon Sep 22 2025
Updated aviation portion for 18Z TAF issuance
.KEY MESSAGES...
- Isolated showers and thunderstorms through early this evening.
  Risk of stronger storms has diminished.
- Areas of fog may develop again tonight. The fog could impact the
  Tuesday morning commute over portions of the area.
&&
.DISCUSSION...
Issued at 214 AM CDT Mon Sep 22 2025
SHORT TERM (Today through Tuesday afternoon)...
Dense Fog/Visibility: Areas of fog have developed across the
eastern half of the forecast area overnight. A Dense Fog Advisory
is in effect for the Fox Valley, the Lakeshore, and far northeast
Wisconsin through 8AM this morning. This fog is expected to
dissipate early this morning as a round of showers moves into the
area. Further west, fog is more patchy due to high clouds
spreading ahead of ongoing convection in western Wisconsin.
Thunderstorms: A round of scattered thunderstorms is anticipated
to move across northern Wisconsin early this morning, with
modestly increased MUCAPES noted on RAP analysis. While these
storms are not expected to be particularly strong, satellite data
indicates decent lightning activity. Additional rounds of
thunderstorms are possible throughout the day as a shortwave
trough tracks across the Upper Peninsula. The HREF shows a warm
front lifting north, roughly into the vicinity of Highway 29, with
1000-1500 J/kg of SBCAPE south of the front. Deep layer shear of
around 30 knots suggests that marginal severe storms are possible,
primarily across central and east-central Wisconsin this
afternoon and evening. The primary hazards will be strong wind
gusts and hail. Brief periods of heavy rain are also possible,
with Precipitable Water values around 1.1 to 1.2 inches.
Determining the exact location of stronger storm development will
be challenging due to morning cloud debris; however, any areas
that experience mostly sunny skies and can destabilize will have
the best chance for storms. Machine learning models, such as the
HRRR Neural Network, have slightly increased the probability for
severe storms, showing 5-10% chances south of Highway 29 this
afternoon and evening. The area should dry out from west to east
on Tuesday as the shortwave moves off to the east. A few showers
may linger into the afternoon across far eastern Wisconsin.
Flooding: The HREF LPMM shows most areas receiving 0.1 to 0.25
inches of rain, though localized areas could see over 1 inch where
heavy precipitation develops. The threat of widespread flooding
remains low, but localized, minor flooding could occur in areas
with poor drainage due to any heavier downpours.
LONG TERM (Tuesday Night through Monday)...
The extended forecast period begins with a transition to drier
conditions. A low-pressure system is progged to develop over the
mid-Mississippi Valley from Wednesday into Thursday. Global
ensemble models have been trending further north with this system,
which has led to an increase in POPs to 15-20% for east-central
Wisconsin on Wednesday afternoon into Thursday. However, the
greatest instability is still expected to be shunted to the south,
which should limit the potential for thunderstorms during this
period. By the end of the week, a ridge is forecast to develop
over Wisconsin, which should bring dry conditions to the region
for next weekend. This ridging is expected to continue into the
start of next week, keeping dry conditions in place. Temperatures
are forecast to remain steadily above normal through the weekend
and into the first half of next week.
&&
.AVIATION...for 18Z TAF Issuance
Issued at 1232 PM CDT Mon Sep 22 2025
Dense fog from earlier this morning over northeast and
east-central WI has diminished, leaving light fog and IFR to low
VFR cigs. Majority of showers and storms have shifted east with
only isolated showers re-developing over parts of northeast WI,
mainly northwest of the Fox Valley. Still a risk of pop-up showers
and storms during peak heating so kept a PROB30 at RHI/GRB/ATW
and MTW late this afternoon/early this evening.
Later tonight, another round of low stratus and fog is poised to
develop. Signal is not as strong for widespread fog, but have
included mention of for and stratus at most TAF sites overnight
into Tuesday morning. Even after fog/lower vsby diminish, appears
that IFR stratus will persist much of the day due to cool moist
northeast flow off Lake Superior and Lake Michigan.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....GK
AVIATION.......JLA

NWS GRB Office Area Forecast Discussion