418
FXUS63 KGRB 191924
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
224 PM CDT Sun Jul 19 2026

.KEY MESSAGES...

- Level 3 of 5 risk of severe storms Monday, including risk for damaging
  winds, large hail, and a few tornadoes. Highest risk is late
  afternoon and early evening.

- Smoke visibility and air quality impacts continue into Monday.

- Drier and cooler for mid-week.

&&

.DISCUSSION...
Issued at 225 PM CDT Sun Jul 19 2026

Severe Storm Potential Monday:

Anomalously strong deep wind fields for late July combined with
ample instability and ascent from an approaching shortwave trough
and cold front will provide a very conducive environment for severe
storms on Monday.

Early day warm advection driven showers/storms may impact the area,
however these will be ahead of the greater instability, so the
overall severe weather risk appears low during this time.

The higher risk for severe weather will be late in the afternoon
into the evening as forcing from the approaching trough and cold
front increase and erode a stout capping inversion. Overall,
19.12Z convection allowing models suggest generally scattered
storm development after 3 or 4 pm with storms moving
southeastward. Given the elongated hodographs, supercell mode or
bowing segments may be favored with a risk of all hazards,
including hail of at least 2 inches and significant winds. Low-
level winds remain southwesterly, but enough speed shear is
forecast to increase low-level shear. Tornadic potential may be
increased with any right-moving supercells. Some guidance
suggests preferred corridors for more organized storm
development within a broader area from northern Iowa northward
through Wisconsin and the UP. These trends will be evaluated
leading up to the event.

Although high rain rates will accompany storms, the scattered nature
of the storms and progressive movement likely will limit
widespread higher rain amounts, but localized 2 inch amounts
could occur. Urban areas or poor drainage areas will be
susceptible to higher rain rates and localized flooding.


Smoke:

Smoke from wildfires to the north continues to impact the area today
within the ridge of high pressure with continued visibility/air
quality impacts. Some gradual improvement in visibility has
been occurring today with diurnal mixing, with more substantial
improvement suggested by the RRFS/HRRR through the day on Monday
as winds increase out of the south ahead of the cold front.


Rest of the week:

High pressure builds south behind the cold front providing cooler
and drier weather for mid-week. By late week into next weekend, mid-
level ridging is forecast to build eastward from the Rockies with
gradually warming temps. No strong signal for precipitation is
apparent late week with low predictability in placement of any
smaller scale shortwave troughs.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1108 AM CDT Sun Jul 19 2026

At KOSH...high pressure across eastern Wisconsin as resulted in
poor mixing this morning, thus slower improvement in visibilities.
Visibilities should slowly improve this afternoon up to 3 to 4
miles by late afternoon. Watching cumulus field to the east of the
airfield which was moving westward, but was struggling to
maintain a broken deck. Have included a tempo group for MVFR CIGS
between 2,500-3,000 feet until 21z. Otherwise, areas of smoke will
continue tonight with visibilities between four and six miles. On
Monday, the first cluster of showers and thunderstorms will
approach the site between 16z-18z Monday. Currently have a PROB30
group for this event as the showers and storms will be on the
weakening trend, and it is possible the showers and storms could
dissipate or move just south of the airport. Also, the weakening
showers may also produce gusty winds from the northwest for an
hour Monday morning, which is not in the 18z TAF. Later Monday
afternoon into the evening, will need to watch round of strong or
severe storms across northeast WI. These storms have the
capability of producing a high end wind event with gusts of 60+
knots along with large hail and torrential rainfall.

For the rest of northeast WI, smoke will continue to gradually improve
through the afternoon and tonight. Some patchy MVFR CIGS will
likely rise into the VFR category this afternoon. The first round
of showers and storms will move into central and north-central WI
after 13z, then continue to move southeast and weaken through the
late morning. Some stronger storms with hail and gusty winds are
possible in north-central and central WI. Meanwhile, later Monday
afternoon and evening, a round of strong or severe storms is
expected with large hail, a high end wind event of gusts of 60+
knots and heavy rainfall.

&&

.MARINE...
Issued at 225 PM CDT Sun Jul 19 2026

South to southwest winds will increase tonight into Monday, with
gusts to 30 kts likely Monday afternoon. Waves on Lake Michigan
will build to 4-7 ft on Monday, and to 2-4 ft on the bay. A Small
Craft Advisory has been issued. A Beach Hazards Statement has
also been issued.

Wildfire smoke will also continue to impact Green Bay and Lake
Michigan through least Monday morning, dropping visibilities to
around 1NM at times. The Dense Marine Smoke Advisory continues
into tonight.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement from Monday morning through Tuesday
     morning for WIZ022-040-050.
MARINE...Dense Smoke Advisory until 7 AM CDT Monday for LMZ521-522-
     541>543.
     Small Craft Advisory from 7 AM Monday to 1 AM CDT Tuesday for
     LMZ521-522.
     Small Craft Advisory from 10 AM Monday to 7 AM CDT Tuesday for
     LMZ541>543.

&&

$$

DISCUSSION...JM
AVIATION...Eckberg
MARINE...JM