672
FXUS63 KGRB 040915
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
415 AM CDT Mon Aug 4 2025

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Wildfire smoke will continue to result in poor air quality and
  reduced visibilities early this week. An Air Quality Advisory
  is currently in effect until noon, but may be extended.

- Patchy fog may restrict visibilities for motorists at times
  early this morning and again overnight into Tuesday morning.

- Temps, humidity and chances for showers/storms slowly increase
  through the week, with highs approaching 90 by weeks end.

&&

.DISCUSSION...
Issued at 413 AM CDT Mon Aug 4 2025

Wildfire smoke will continue to impact the region today and
tonight, bringing hazy skies, minor restrictions in visibilities,
a burning smell at the surface at times, and poor air quality.
Vertically integrated and near-surface smoke forecasts from the
HRRR, RAP and Canadian show the large area of smoke remaining in
place over northeast WI as it is trapped/stuck under a high
pressure system. On Tuesday, models suggest the smoke may be
confined more to eastern WI, with the majority of the smoke
shifting north of the area on Wednesday as stronger southerly flow
arrives. Continued with areas of smoke and haze across the entire
area today into tonight, but kept it mainly across the east on
Tuesday. The Air Quality Advisory remains in effect until noon
today and may be extended by the DNR later this morning.

Patchy ground fog is expected early this morning and possibly
again overnight into Tuesday morning. The ground fog could be
locally dense. Any fog will mix out within a hour or two of
sunrise.

High pressure will slowly weaken and shift east of the Great
Lakes today, with chances for showers/storms increasing into mid-
late week. Threw in a small chance (15-20%) over north central WI
later today as some models clip this area with a little light
precip this afternoon, as a weak shortwave crosses the area and
a lake breeze drops south from Lake Superior. But soundings still
look quite dry, so any activity should be light and very isolated.
Otherwise, it is looking dry today into Tuesday morning. Models
have been hitting at the possibility of some spotty showers
during peak heating on Tuesday as moisture levels tick up. But
with a weak capping inversion around 10,000 ft in place, thinking
that should be enough to hold down or keep any activity very
isolated. Prefer to keep a dry forecast for now with just some
5-14% PoPs. Some of this daytime popcorn activity is possible on
Wednesday as well. As zonal flow sets up over the northern CONUS
mid-week, a couple shortwaves will likely touch of areas of
showers and storms across the Upper Plains and Midwest. These will
make a run at the area Wednesday into Thursday, but most guidance
has the activity staying just to our west on Wednesday, with a
better chance (up to ~40%) of a weakening area of showers/storms
making it to our area on Thursday (as PWATs climb above 1.5"),
especially across central and north central WI. Better chances
(35-55%) of organized storm activity arrives late this weekend as
a stronger shortwave and cold front drop across the region.

As flow turns southerly, temps and humidity levels will slowly
tick up through the week. Just how hot we get will likely be
determined by cloud cover and precip coverage, but ENS/GEFS
showing probabilities of 90+ degrees in the 30-70% range, highest
on Saturday across central and eastern WI. As dewpoints climb, so
will heat indices, with upper 80s and 90s forecast for Friday
into Saturday. This will push the Heat Risk into the Major
category (level 3 out of 4).

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1038 PM CDT Sun Aug 3 2025

Surface-based smoke will continue to lower vsbys at times
throughout this TAF period, fluctuating between VFR and MVFR. In
addition to the reduced vsbys from smoke, ground fog is expected
to develop overnight into Monday morning, causing vsbys to drop
to the VLIFR/LIFR category at times.

While the hazy skies from the smoke will continue throughout this
TAF period, high clouds will also move across the region, with
the potential for some fair weather cu developing Monday
afternoon.

&&

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

&&

$$

DISCUSSION.....Bersch
AVIATION.......Kruk