Green Bay, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

778
FXUS63 KGRB 260727
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
227 AM CDT Sun Jul 26 2026

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Heat indices approaching 100 degrees across central Wisconsin
  this afternoon, where a Heat Advisory is in effect for Wood,
  Portage, Waupaca, and Waushara counties.

- Strong to severe thunderstorms are possible mid to late this
  afternoon through late this evening, and again on Monday
  afternoon and evening. Damaging winds and large hail will be the
  primary hazards.

- A cold front passing through the region will bring a shift to
  northerly winds and relief from the high humidity for Tuesday
  through mid-week, with lower thunderstorm chances until late in
  the work week.

&&

.DISCUSSION...
Issued at 226 AM CDT Sun Jul 26 2026

The latest RAP analysis and satellite/radar imagery show a potent
sub-tropical ridge centered over the Intermountain West and
central Great Plains early this morning. The leading edge of a
very warm and muggy airmass stretches along a warm front extending
from central Minnesota to southwest Wisconsin. The active ring of
fire convective pattern around the ridge has maintained
thunderstorm clusters from Montana down into Iowa and Minnesota
overnight. Across north-central and northeast Wisconsin, low
stratus has been gradually eroding from west to east early this
morning, promoting areas of locally dense ground fog across north-
central Wisconsin. Will be monitoring trends for a Dense Fog
Advisory. The clearing trend should continue through dawn before
cloud debris from Minnesota storms drifts overhead. Elevated
moisture convergence translating eastward may drive a few dying
showers into central Wisconsin early, but most activity should
fizzle or stay southwest of the forecast area.

Heat and Humidity Today through Monday...
As the warm front lifts northeast across the region today, hot
and muggy conditions will overspread north-central and northeast
Wisconsin. Model time-height cross sections show low-level clouds
dissipating by mid-morning, allowing strong diurnal heating to
boost temperatures into the upper 80s and lower 90s from the Fox
Valley and Bayshore westward. Lake Michigan shoreline areas will
remain cooler in the low to middle 80s due to lake influence.
Combined with dewpoints surging into the lower 70s, heat index
values will reach near 100 degrees this afternoon across parts of
central Wisconsin. A Heat Advisory has been issued for Wood,
Portage, Waupaca, and Waushara counties. Wildfire smoke aloft may
limit surface insolation slightly, but even accounting for a minor
temperature reduction, heat indices near 100 degrees remain
likely. Temperatures on Monday will be slightly cooler, but heat
indices will still approach the middle 90s.

Severe Thunderstorm Potential Tonight and Monday...
While warmed temperatures aloft will keep the forecast area
capped and largely dry through late afternoon, the combination of
intense heating, the advancing warm front, and a weak shortwave
impulse is expected to trigger explosive convective development
over northern Minnesota late this afternoon. Storms are forecast
to grow upscale into one or more convective clusters that will
race southeast into north- central Wisconsin during the evening
and overnight hours. Damaging wind gusts will be the primary
threat with these clusters, though isolated large hail will be
possible when storms first arrive into northern WI. Storms will
weaken overnight as they move east, but warm advection could keep
lingering elevated showers and non- severe storms in place into
Monday morning.

On Monday, another shortwave trough and cold front will traverse
the western Great Lakes. Model guidance indicates favorable severe
parameters with 2000-3000 J/kg of ML CAPE and 40+ knots of deep
layer shear. Convective evolution on Monday carries moderate
uncertainty due to potential cloud cover and morning rain debris,
but where sufficient surface heating occurs, organized storms
capable of large hail and damaging winds could develop along the
front.

Long Term...Tuesday through Saturday
Winds will shift to the north on Tuesday in the wake of the cold
front, bringing an end to the oppressive humidity even as daytime
highs remain slightly above normal in the 80s. Surface high
pressure will build into the Upper Great Lakes on Tuesday and
persist through Thursday, yielding an extended stretch of dry,
pleasant weather with seasonable temperatures. The next shortwave
trough and associated frontal boundary are scheduled to arrive
late Thursday night into Friday, bringing the next widespread
chance for showers and thunderstorms to north-central and
northeast Wisconsin. Near to slightly above normal temperatures
are forecast for next weekend.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1127 PM CDT Sat Jul 25 2026

The VFR/MVFR stratus is clearing out, making way for fog to form
across areas that have cleared. North-central Wisconsin has fallen
to LIFR/VLIFR with the fog, with the central Wisconsin airports
expected to fall to at least IFR overnight. Further south across
east-central Wisconsin fog is less certain as the clouds are
hanging in a bit more than further north. Any fog that develops
should dissipate shortly after sunrise Sunday. Skies are expected
to also clear out sometime Sunday morning.

There is a chance for an area of thunderstorms to develop and
track through the region Sunday and Sunday night. However, timing
and exact placement are too uncertain to include in this set of
TAFs. There is another chance on Monday as well, which could hinge
on what happens on Sunday.

.KOSH...

Stratus over OSH looks to stick around overnight as an inversion
continues to lower. CIGS will start out VFR, then lower to MVFR
overnight as the inversion lowers. These clouds are expected to
dissipate Sunday morning around 16-18Z with VFR conditions the
rest of the day. Steady south to southwesterly winds around 4-8
kts is expected through Sunday. The risk for any showers or
thunderstorms impacting OSH Sunday afternoon and evening is too
low to include in this set of TAFs.

There is a chance for patchy fog to develop in the Fox Valley
early Sunday morning. Given the recent MOS trends will introduce
some MVFR/IFR fog at OSH with this set of TAFs overnight into
Sunday morning. Any fog should dissipate shortly after sunrise on
Sunday.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon today to 9 PM CDT this evening for
WIZ035>037-045.
&&

$$

DISCUSSION.....MPC
AVIATION.......Kurimski