Special Weather Statement, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
658 AM CDT Tue Jun 30 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- The dangerous heat peaks today, but the high heat and humidity
  will continue through late this week, resulting in continued
  heat-related impacts. An Extreme Heat Warning is in effect
  through 7 PM today (Tuesday) for central, east-central, and far
  northeast Wisconsin. A Heat Advisory is in effect for north-
  central Wisconsin for the same time period.

- Periodic chances for thunderstorms expected at times this week.
  Some of these storms could become strong or severe. Main
  hazards would be damaging winds, large hail, and heavy rain.

- Gusty onshore southerly winds will result in high waves and
  dangerous currents on Lake Michigan beaches through late this
  evening.

&&

.DISCUSSION...
Issued at 300 AM CDT Tue Jun 30 2026

Precipitation/Thunder Chances...An upper-level ridge axis was
focused over the western Great Lakes early this morning, while a
ridge rider (shortwave) was moving over MN. As a result, severe
weather was ongoing in northeast MN. Meanwhile, over our forecast
area, satellite and radar imagery showed areas of low clouds with an
area of light rain and a few rumbles of thunder just to the west of
the forecast area. Given the forecast area is under a large cap, any
of the storms in northeast MN are not anticipated to impact the
forecast area. However, the area of rain and rumbles of thunder will
move into portions of central and north-central WI early this
morning, but are anticipated to dissipate as they move eastward.
Otherwise, much of the day is forecast to remain dry until the
afternoon when a low-level southwesterly jet increases and meets up
with a surface boundary. With a very moist atmosphere (dew points in
the low 70s), deep-layer shear of 30-40 kts, and more than enough
instability, there will be potential for severe thunderstorms to
develop. The latest CAM guidance would suggest convective initiation
beginning in the late afternoon over the forecast area and
continuing through the late evening. Large hail, damaging winds, and
heavy rainfall will be the main threats if these severe storms
develop. There is uncertainty in the coverage as some models suggest
portions of the area may be capped, limiting storm potential.

The boundary associated with today's convection is progged to sag
south over the state tonight and gradually north into Wednesday. As
destabilization occurs during the afternoon and evening, this
boundary will be the trigger for additional thunderstorms to develop
and ride along the instability gradient. However, there is
uncertainty where this boundary will set up. Regardless, there will
still be ample heat and instability to work with to produce some
strong/severe storms during Wednesday afternoon into the late
evening.

Models indicate additional convection may develop on Thursday as the
upper-level ridge breaks down; however this will depend greatly on
the evolution of convection on Wednesday. A greater chance for
showers and thunderstorms appears to be on Friday with the passage
of a mid-level shortwave, but it is too early to determine the
severe potential. There are signs of an additional shortwave
sometime over the 4th of July holiday weekend, but there are timing
and placement differences.

Dangerous Heat...Temperatures early this morning were still in the
low 70s to low 80s across the region with dew points in the 70s. As
a result, heat index values were in the low 80s to low 90s. With the
abnormally warm airmass remaining in place today, continued to keep
the heat headlines as is with the same end time of 7 pm today.
However, given temperatures are progged to be warmer in far
northeast WI, decided to upgrade Menominee, Oconto, Marinette, and
Florence counties into the Extreme Heat Warning. High temperatures
today are expected to climb into the upper 80s to mid 90s across the
region with dew points in the low to mid 70s, resulting in afternoon
peak heat indices ranging from 95 to 110 degrees. Of course,
depending on when and if the convection begins, some locations may
not see these peak values.

High temperatures and dew points on Wednesday will not be as high as
today, keeping heat index values right around 100 mainly for
locations in east-central WI. An additional Heat Advisory may be
needed. With the upper-level ridge breaking down a bit midweek,
temperatures and dew points will again drop slightly, with heat
index values topping out in the 80s or low 90s for the remainder of
the forecast period, including during the 4th of July holiday
weekend. Therefore, aside from Wednesday, the need for additional
heat headlines looks to come to an end through at least the end of
the weekend.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 658 AM CDT Tue Jun 30 2026

A mix of MVFR and VFR cigs prevailed across the region this
morning with the MVFR cigs mainly focused across the central and
north-central WI areas. A few showers have fallen at the RHI TAF
site early this morning as well. Upstream, showers and a few
storms were observed in west-central WI. Confidence is high enough
to include -SHRA at AUW/CWA/RHI in a TEMPO group for this morning,
but not high enough to include the mention of thunder given trends
showing the shower activity dissipating as it moves
east/northeastward.

VFR conditions are anticipated for the remainder of the day and
overnight. However, there are some high-resolution models
indicating isolated to scattered thunderstorms developing in
central or north-central WI this afternoon and evening, but the
atmosphere will be fairly capped. Therefore, confidence is still
not high enough to include a mention in this TAF issuance.

Southwest winds will increase today, with gusts up to 20 kts.
Winds subside late this evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 7 PM CDT this evening for WIZ005-010-011-018-
019.

Extreme Heat Warning until 7 PM CDT this evening for WIZ012-013-
020>022-030-031-035>040-045-048>050-073-074.

Beach Hazards Statement through late tonight for WIZ022-040-050.
&&

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

Hazardous Weather Outlook
National Weather Service Green Bay WI
317 AM CDT Tue Jun 30 2026

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-010830-
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-
317 AM CDT Tue Jun 30 2026

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

.DAY ONE...Today and Tonight

An Extreme Heat Warning is in effect for central, east-central,
and far northeast Wisconsin as well as the lakeshore counties. A
Heat Advisory is in effect for north-central Wisconsin.

There is a chance for strong to severe thunderstorms late this
afternoon into this evening. The main hazards are large hail,
damaging winds, and heavy rainfall.

There is an increased risk of rip currents at Lake Michigan
beaches today.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Daytime heat index values will near or reach 100 degrees on
Wednesday.

Periodic chances for thunderstorms are expected through the
holiday weekend. There is a risk for strong to severe storms
Wednesday and Wednesday night. The main hazards will be large
hail, damaging winds, and heavy rain.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening.

LMZ521-522-541>543-010830-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
317 AM CDT Tue Jun 30 2026

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

.DAY ONE...Today and Tonight

Conditions hazardous to small craft are expected on Lake Michigan
through late this evening due to persistent southerly winds and
building waves.

There is a chance for thunderstorms this morning and again this
evening into tonight. Any thunderstorm would pose a hazard to
mariners.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Periodic chances for thunderstorms will last through the upcoming
weekend. Some of these storms could be strong or severe. Any
thunderstorm would pose a hazard to mariners.

Kruk

Special Weather Statement
National Weather Service Green Bay WI
903 AM CDT Tue Jun 30 2026

WIZ036-037-045-301500-
Waupaca WI-Waushara WI-Portage WI-
903 AM CDT Tue Jun 30 2026

...AN AREA OF STRONG THUNDERSTORMS WILL IMPACT NORTHERN WAUSHARA...
SOUTHEASTERN PORTAGE AND WESTERN WAUPACA COUNTIES UNTIL 10 AM CDT...

At 903 AM CDT, Doppler radar was tracking an area of strong
thunderstorms over Plainfield, or 17 miles northwest of Wautoma,
moving northeast at 45 mph.

HAZARD...Wind gusts up to 40 mph and half inch size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

The strong thunderstorms will be near...
  Plainfield around 905 AM CDT. Hartman Creek State Park around 925
  AM CDT. Chain O' Lakes-King and Amherst around 930 AM CDT. Waupaca
  around 935 AM CDT.

Other locations impacted by these strong thunderstorms include
Hancock, Almond, Bancroft, Heffron, Keene, Blaine, Emmons Creek
Barrens, Sheridan, King and Rural.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the weather situation closely and be alert for threatening
weather conditions.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4425 8968 4432 8971 4459 8890 4412 8889
      4408 8960 4425 8960
TIME...MOT...LOC 1402Z 240DEG 37KT 4423 8954

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

JG

Special Weather Statement
National Weather Service Green Bay WI
929 AM CDT Tue Jun 30 2026

WIZ030-036-301515-
Portage WI-Marathon WI-
929 AM CDT Tue Jun 30 2026

...AN AREA OF STRONG THUNDERSTORMS WILL IMPACT NORTHERN PORTAGE AND
SOUTHEASTERN MARATHON COUNTIES UNTIL 1015 AM CDT...

At 929 AM CDT, Doppler radar was tracking an area of strong
thunderstorms near Stevens Point, moving east at 35 mph.

HAZARD...Wind gusts up to 40 mph and half inch size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

The strong thunderstorms will be near...
  Whiting around 930 AM CDT. Stevens Point around 935 AM CDT.

Other locations impacted by these strong thunderstorms include
Plover, Park Ridge, Dewey Marsh Wildlife Area, Jordan, Stockton,
Ellis, North Star, Polonia, Custer and Shantytown.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the weather situation closely and be alert for threatening
weather conditions.

&&

LAT...LON 4451 8973 4468 8973 4480 8923 4456 8922
      4444 8922 4439 8973
TIME...MOT...LOC 1429Z 254DEG 29KT 4456 8961

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

JG