291
FXUS63 KGRB 122326
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
626 PM CDT Sat Jul 12 2025

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Smoke will impact the region through the weekend. The smoke will
  mix down to the surface at times, reducing visibilities to 2 to
  5 miles, and negatively impacting air quality. An Air Quality
  Advisory is in effect through noon on Monday.

- Next round of active weather arrives Tuesday afternoon into
  Wednesday.

&&

.DISCUSSION...
Issued at 311 PM CDT Sat Jul 12 2025

Precipitation/Thunderstorm Chances: Despite the fairly decent
instability (up to ~1500 J/kg) and deep layer shear (30-45 kts), a
weak capping inversion and limited surface convergence, along
with the best upper forcing and steeper lapse rates trailing the
front, is limiting storm intensity and coverage this afternoon. As
a little more heat/instability builds and a weak cool front works
east, expect the broken line of showers and isolated storms to
move across far eastern WI. With DCAPE up to 700 J/kg (although
the highest values are behind the line of showers), any organized
storm could produce some gusty winds, along with brief torrential
rain. No flooding is expected as the storms will be quick movers.
The line will exit to our east by 5-6pm, with dry conditions
expected tonight.

A weak boundary will approach central and north central WI late
on Sunday, which could produce a stray shower or storm. Have keep
the slight chance (20%) PoPs in the early evening. Another very
small chance of a shower on Monday as this boundary lingers in the
area and a weak shortwave crosses the state, but kept most of the
area dry for now. A dying complex of storms will make a run at
north central WI early Tuesday, with better chance for widespread
shower and storms later Tuesday into Wednesday as the boundary
sags over the area, instability and moisture pool south of the
boundary, a LLJ points into the region, and a couple quick moving
shortwaves within the zonal upper flow.

Smoke: Satellite showing a large area of smoke across the Upper
Midwest, along with many surface reports of haze. Webcams also
showing a pretty milky/hazy sky. HRRR/RAP/Canadian smoke guidance
all showing the elevated smoke over the region into Sunday, with
another batch possible on Monday. The smoke could make it to the
surface at times, especially across northern WI. Very poor air
quality readings have been observed across MN today and should
shift east tonight into Sunday. An Air Quality Advisory remains
in effect through noon on Monday.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 615 PM CDT Sat Jul 12 2025

Reduced VSBYs due to near-surface smoke will be the primary
aviation concern.

Showers and isolated storms have pushed east of the region with
the passage of a cold front. Smoke was mixing to the surface in
the wake of the frontal passage, and reducing VSBYs to 2-5SM
in many locations. The smoke will impact the region through the
TAF period. Have attempted to provide some resolution when
possible, including the potential for a break in the near-surface
smoke over C/EC later this evening into Sunday morning, and for
IFR VSBYS during periods of higher smoke concentrations.
Expecting dry conditions through the period, with only SCT daytime
cumulus development.

Gusty west winds will subside by sunset, then become a bit gusty
again on Sunday.

&&

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

&&

$$

DISCUSSION.....Bersch
AVIATION.......Kieckbusch