Small Craft Advisory 69, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
122 PM CDT Fri Jul 31 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Widespread rain with a few thunderstorms will overspread north-
  central and northeast Wisconsin through Saturday morning. No
  severe weather is expected.

- There is an increased risk for rip currents along Lake Michigan
  beaches south of Sturgeon Bay on Saturday night and Sunday.

- Quiet weather returns Saturday night through Monday.

- Scattered showers and thunderstorms return Tuesday and Wednesday
  as a cold front moves through the region.

&&

.DISCUSSION...
Issued at 106 PM CDT Fri Jul 31 2026

A 1006 mb surface low centered over northern Iowa early this
afternoon will track slowly southeast toward central Illinois
tonight, before continuing eastward into the Ohio Valley on
Saturday. An arcing band of warm advection rainfall is currently
spreading northeast across southwest Wisconsin. Lightning is
relatively sparse over the northern Mississippi Valley so far
today, and radar returns have been weakening as they move closer
to central Wisconsin. Another area of light rain is occurring over
far northern WI and the Upper Peninsula along a 700mb gradient.
As this low moves across the region, rain and thunderstorm trends
remain the focus of this forecast.

Rainfall will continue to lift northeast and intensify through
early this evening as low-level warm advection strengthens
downstream of the Iowa low. While the overall boundary layer
remains relatively stabilized by widespread cloud cover and
earlier rain, isolated storms cannot be ruled out and most likely
near the U.P. border. The rain will likely continue over northeast
Wisconsin through Saturday morning before ending. With daytime
heating, a few widely scattered showers could also develop in the
afternoon from central to far northeast WI.  The highest
probabilities for 1 inch or greater of rainfall (30-50%) remain
situated south of a Marshfield to Green Bay line, with the highest
confidence in localized 1-inch amounts extending from Wautoma
toward Manitowoc. Highs on Saturday will be held in the 70s under
cloud cover and persistent northeast winds.

Surface high pressure will build into the Upper Great Lakes
Saturday night and remain dominant through Monday night. This will
yield clear to partly cloudy skies, light winds, and pleasant
mid-summer conditions. High temperatures will steadily warm from
the mid and upper 70s on Sunday to the lower and mid 80s on Monday
under ample sunshine.

The next notable weather system arrives Tuesday into Wednesday as
an upper-level shortwave trough and associated surface cold front
push east across the Northern Plains into the Upper Midwest.
Moisture return ahead of the boundary will push dew points back
into the 60s, generating MUCAPE of 500-1000 J/kg and deep-layer
shear of 25-30 knots. This environment will bring scattered
showers and thunderstorms from Tuesday afternoon through Wednesday
morning. While severe weather risk remains low at this time due to
modest instability, parallel flow aloft relative to the frontal
boundary could result in localized training of shower activity.
Lighter precipitation chances linger into Thursday as cooler,
near-normal air settles back over the region with highs returning
to the upper 70s and lower 80s.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1209 PM CDT Fri Jul 31 2026

Low pressure will be traveling southeast from the northern
Mississippi Valley to central Illinois and Indiana tonight. North
of the low track, periods of light to moderate showers and
embedded thunderstorms will bring deteriorating flight conditions
to the region through the afternoon into the evening. Brief IFR
visibilities will be possible in the heavier shower activity.
Coverage of thunderstorms will be relatively low, but highest
coverage will likely be found near the Upper Peninsula border that
could impact RHI.

As ceilings lower in the steadier rain, probabilities for MVFR
ceilings will increase this evening over central and east-central
WI and across much of the area overnight. These ceilings will be
slow to rise over east-central WI on Saturday morning where light
rain is expected to persist.

Some guidance develops lower visibilities over far northern
Wisconsin late tonight into Saturday morning. As a consequence,
added a tempo group for IFR visibilities at RHI.

The low clouds are expected to develop into a broken cloud field
on Saturday will high end MVFR to low end VFR ceilings expected
through early afternoon.

&&

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

&&

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

Hazardous Weather Outlook
National Weather Service Green Bay WI
122 PM CDT Fri Jul 31 2026

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-011830-
Vilas-Oneida-Forest-Florence-Northern Marinette County-Lincoln-
Langlade-Menominee-Northern Oconto County-Door-Marathon-Shawano-
Wood-Portage-Waupaca-Outagamie-Brown-Kewaunee-Waushara-Winnebago-
Calumet-Manitowoc-Southern Marinette County-
Southern Oconto County-
122 PM CDT Fri Jul 31 2026

This Hazardous Weather Outlook is for north-central and northeast
Wisconsin.

.DAY ONE...This Afternoon and Tonight

Widespread rain along with isolated thunderstorms are expected.
No severe weather is anticipated, but there is a marginal risk
for excessive rainfall due to the potential for localized
flooding.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

There is an increased risk for rip currents along Lake Michigan
beaches on Saturday night and Sunday.

There is a chance of thunderstorms on Tuesday afternoon and
Tuesday night.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed this afternoon or tonight.

LMZ521-522-541>543-011830-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
122 PM CDT Fri Jul 31 2026

This Hazardous Weather Outlook is for portions of northwest Lake
Michigan and the waters of Green Bay.

.DAY ONE...This Afternoon and Tonight

Isolated thunderstorms will be possible through tonight. Any
thunderstorm could pose a hazard to mariners.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Hazardous conditions to small craft will be possible on Saturday
night and Sunday due to gusty northeast winds and high waves.

Thunderstorms will be possible on Tuesday night. Any thunderstorm
could pose a hazard to mariners.

MPC