Dunbar, Wisconsin Weather Forecast Discussion

296
FXUS63 KGRB 221059
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
559 AM CDT Mon Sep 22 2025
Updated aviation portion for 12Z TAF issuance
.KEY MESSAGES...
- Shower and thunderstorm chances will continue through much of
  today. There is a Marginal Risk for severe storms capable of
  producing strong wind gusts and hail this afternoon and evening.
- Areas of fog have developed overnight and are expected to linger
  through the early morning. The fog may be locally dense with the
  visibility of 1/4 mile. The fog may impact the morning commute
  to work or school.
&&
.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 12Z TAF Issuance
Issued at 559 AM CDT Mon Sep 22 2025
IFR/LIFR conditions are present early this morning across eastern WI
where dense fog has developed overnight. Further west rain showers
have moving into central Wisconsin which is keeping the fog more
patch in those area. As these showers continue to move north and
east this morning they should help dissipate the fog and low stratus
with conditions expected to improve to MVFR/VFR by late morning.
Another round of thunderstorms will be possible this afternoon and
evening with isolated strong storms possible south of AUW to GRB
line. The strongest storms may produce strong wind gusts, hail, and
periods of heavy rain resulting in reduced visibility. Have framed
out the best timing for these storms with PROB30 groups at all the
TAF sites.
Tonight fog/IFR status are likely to redevelop, however, the extend
is rather uncertain as it will be dependent on where and when rain
and cloud cover are able to clear out.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 8 AM CDT this morning for WIZ012-013-
020-022-031-037>040-048>050-073-074.
&&
$$
DISCUSSION.....GK
AVIATION.......GK

NWS GRB Office Area Forecast Discussion