748
FXUS63 KGRB 040358
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1058 PM CDT Mon Aug 3 2026

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- A cold front will bring a chance for showers and thunderstorms
  Tuesday into Tuesday evening. The threat for severe weather
  remains low.

- There is a 20-35% chance of rain lingering Wednesday and
  Wednesday night across east-central Wisconsin and the lakeshore.
  The severe weather risk will remain low.

- Warmer and more humid conditions build into the area over the
  weekend, along with periodic chances for showers and
  thunderstorms Friday night through Sunday.

&&

.DISCUSSION...
Issued at 127 PM CDT Mon Aug 3 2026

The latest RAP analysis and satellite/radar imagery show high
pressure centered over southern Lake Michigan to northern Illinois
early this afternoon, bringing quiet conditions across northeast
Wisconsin. High clouds continue to stream in from the northwest
ahead of thunderstorm activity over the northern Plains. Upstream,
a cold front stretches from northern Minnesota south-
southwestward into eastern Colorado. High pressure will shift to
the eastern Great Lakes tonight, allowing the cold front to move
into northwest Wisconsin late tonight and traverse the area on
Tuesday.

The main weather focus in the short term is the cold frontal
passage on Tuesday. High pressure shifting east tonight will
maintain dry conditions through early Tuesday morning, though high
clouds will gradually thicken. The cold front will enter
northwest Wisconsin after 4 AM Tuesday, with post-frontal showers
reaching north-central Wisconsin after 7 AM. Convergence along
the front appears relatively weak as it moves through during the
late morning and afternoon. Forecast soundings indicate a stout
capping inversion in the 800-700 mb layer that will suppress
deeper convection for much of the day, keeping most activity in
the form of post-frontal showers along the boundary. As the cap
begins to erode late Tuesday afternoon into the evening, some
convective- allowing models produce widely scattered thunderstorms
across northeast Wisconsin. If storms develop, convective
parameters look modest with skinny CAPE profiles of 500-1000 J/kg
and deep-layer shear peaking at 20-25 kts, keeping the threat of
severe weather low.

By Tuesday evening, the frontal boundary is expected to become
more active from Iowa into southern Wisconsin within a developing
frontogenesis zone. Precipitation is forecast to track northeast
along the front overnight into Wednesday. Latest guidance over the
past 24 hours has trended further south with the heaviest rainfall
axis, keeping the significant precipitation across southern
Wisconsin. Consequently, rain chances have been lowered to 20 to
35 percent across east-central Wisconsin on Wednesday, with dry
conditions expected elsewhere.

A slow-moving, flattened upper trough will slide across the region
Thursday through Friday. Thursday will remain mostly quiet before
the next cold front approaches late on Friday, increasing the
probability of showers and storms Friday afternoon and night. This
front will serve as the focus for periodic shower and thunderstorm
chances through the weekend, though confidence in exact timing
from Friday through Sunday remains low. Model guidance has trended
warmer and more unstable for Saturday and Sunday as the upper
trough lifts north and mid-level heights rebound, allowing heat
and humidity from the western ridge to push into northeast
Wisconsin. These trends will be monitored for severe potential
over the weekend, though deep-layer shear currently appears
relatively weak.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1058 PM CDT Mon Aug 3 2026

VFR conditions are expected through early Tuesday morning as high
clouds gradually increase over the area late tonight into Tuesday
morning ahead of the next cold front. A brief period of LLWS is
possible at the central and north-central WI TAF sites mainly
between 06-13z Tue.

As the cold front moves over the region Tuesday morning, clouds
will thicken with MVFR cigs at the central and north-central WI
TAF sites. There is uncertainty in these MVFR cigs reaching the
east-central WI TAF sites as the clouds should gradually rise
as the front moves east during the day, but will likely remain as
low-end VFR cigs. A broken line of showers and storms seen
upstream in MN late this evening is expected to gradually weaken
as it moves eastward into Tuesday morning. Included a TEMPO group
at RHI with PROB30 groups at the central WI TAF sites all for
showers for Tuesday morning. Some hi-res models suggest
redevelopment of the showers occurring as the front reaches the
east-central WI TAF sites Tuesday afternoon, so have included
PROB30 groups for now. Cannot rule out the potential for a few
rumbles of thunder, but confidence is too low to include thunder
in this TAF issuance.

Southwest winds under 10 kts through tonight, increasing Tuesday
morning with gusts to 15-20 kts before veering to the west and
decreasing behind the front Tuesday afternoon and evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from Tuesday afternoon through Tuesday
evening for WIZ022-040-050.
&&

$$

DISCUSSION.....MPC
AVIATION.......Kruk

NWS GRB Office Area Forecast Discussion