Dancy, Wisconsin Weather Forecast Discussion

082
FXUS63 KGRB 220407
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
1107 PM CDT Sun Sep 21 2025
Updated aviation portion for 06Z TAF issuance
.KEY MESSAGES...
- On and off chances for showers and thunderstorms late tonight
  through Monday. Best chance for a few strong storms is Monday
  afternoon and evening where quarter size hail and strong wind
  gusts are possible.
- Areas of fog are expected tonight, especially after midnight and
  then linger into Monday morning. The fog may be locally dense
  with the visibility of 1/4 mile possible. The fog may impact the
  morning commute to work or school.
&&
.DISCUSSION...
Issued at 310 PM CDT Sun Sep 21 2025
SHORT TERM (Today through Monday afternoon)
Scattered showers and isolated thunderstorms continued this
afternoon, with a few of them producing brief locally heavy rain.
The showers and storms should diminish and then end around
sunset. Later this evening and overnight, areas of fog will
develop with locally dense fog possible at times. The HREF
was indicating probabilities of 40-70% that the visibility
will drop below one mile tomorrow morning. The probabilities
were pretty similar for 1/4 mile as well. Also overnight,
an upper level disturbance will bring another round of showers
and perhaps a thunderstorm across north-central WI that could
impact the fog. On Monday, scattered thunderstorms are expected
as the upper level disturbance moves over the state. Bufkit
soundings indicated around 1,000 J/KG of CAPE, 0-6 km shear
values around 30 knots to support stronger storms. The
Storm Prediction Center Day 2 outlook has a Marginal Risk of
severe storms, generally south of Highway 29. Will mention
the risk of a severe storm in the Hazardous Weather Outlook.
LONG TERM (Monday Night through next weekend)
Any lingering storms Monday afternoon should come to an end
Monday evening. Overnight, areas of fog are expected. The fog
may be locally dense. Confidence is moderate to high based
on numerical guidance supporting fog. From Wednesday through
Sunday, above normal temperatures are expected. By late
September, the normal high drops into the 60s. NBM probabilities
of highs reaching 70 each day ranged from 40-70% across the north
and 50-80% over the south. The only concern will be Wednesday
into Thursday as the ECMWF has shifted the system northward over
the last few days. May need to add or increase the chance of rain
for this period. Dry conditions should prevail Friday through
Sunday.
A short-wave trough and its associated surface boundary are
forecast to exit the region Monday night into early Tuesday
morning. A few lingering showers may persist Monday night, but
the area is expected to dry out by mid-Tuesday morning as a
surface high-pressure system builds in from the west and brings
in drier air. Ensemble guidance from various models supports this
pattern, showing continued height rises along the U.S./Canadian
border through the middle of the week, which should keep the
forecast area mostly dry.
The next synoptic feature of note is a surface low that is
progged to develop over the Ozarks during the middle of next
week. This low is then forecast to lift northeast, tracking
toward the eastern Great Lakes region from Thursday into Friday.
While some moisture wrapping around this system could potentially
bring a few showers to the lakeshore late in the week, the
primary axis of better moisture and instability is expected to
remain shunted well to the south of our forecast area.
Temperatures throughout this extended period are expected to
remain steady, holding at or just above normal for this time of
year. The overall pattern appears to favor a relatively tranquil
period with minimal impactful weather.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1106 PM CDT Sun Sep 21 2025
Next round of showers (40-60% chance) and some storms (20-40%
chance) arrive late tonight into Monday morning. Gusty winds,
small hail and heavy downpours could accompany the storms, though
confidence in those details is too low to include right now. Have
increased SHRA and TSRA potential in this latest round of TAFs
though. Another round of scattered showers and storms may develop
in the afternoon as well, though current indications are strongest
storms will stay south of all the terminals.
Other issue into Monday morning will be low stratus and fog that
has developed this evening. Expect areas of fog overnight, with
1SM vsby, down to 1/2SM or less at times. Have hit the fog harder
with the latest TAFs based on recent observations. Other than the
showers and storms on Monday, LIFR-IFR conditions and fog will
improve to MVFR/VFR through the day. Winds will be light through
the TAF period.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 8 AM CDT Monday for WIZ012-013-022-
038>040-048>050-073-074.
&&
$$
DISCUSSION.....Eckberg
AVIATION.......JLA

NWS GRB Office Area Forecast Discussion