Severe Thunderstorm Warning 86, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
211 PM CDT Tue Jun 30 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Dangerous heat peaks this afternoon. An Extreme Heat Warning is
  in effect through 7 PM today for central, east-central, and far
  northeast Wisconsin, with a Heat Advisory is in effect
  elsewhere. Additional heat headlines may be needed Wednesday.

- Scattered storms late this afternoon into this evening, with
  isolated severe storms. Greater chances for severe weather for
  Wednesday, especially during the afternoon into evening hours.
  This is now looking like a higher-end severe threat with most
  area now in an Enhanced Risk (level 3 of 5).

- Heavy rain potential Wednesday into Wednesday night. At least
  isolated instances of flash flooding possible.

- Additional chances for thunderstorms through Friday, with
  chances beginning to diminish for the holiday weekend.

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

&&

.DISCUSSION...
Issued at 210 PM CDT Tue Jun 30 2026

Precipitation/Thunder Chances...Morning round of storms has exited.
Given minimal large scale forcing interacting with MLCAPEs up to
4000J/kg, expect scattered storms to form late this afternoon
through this evening, potentially emerging from blossoming cu
field from northeast IA into southern WI. With a very moist
atmosphere (dew points in the low 70s) resulting in extreme
instability, deep-layer shear of 30-40 kts, severe thunderstorms
may occur. Coverage of storms is the main question due to the
capping across our area that was only enhanced by the morning
convection. Large hail, damaging winds, and heavy rainfall will
be the main threats.

Late tonight into Wednesday morning, good signal that shortwave on
leading base of plains trough, along with increasing 850mb-500mb
jets will trigger scattered storms in the morning lifting across
the area. There may be a break, then additional severe storms are
expected to develop due to interaction with outflow from morning
storms and approaching trough. These triggers will interact with
MUCAPEs up to 3000J/kg and effective shear 50+ kts. Overall a
higher-end severe risk is emerging with bowing structures and
potential supercells. Thus, there is a potential for all hazards,
including wind gusts over 70 mph, hail to golf-ball sized, and
isolated tornadoes. At this point, the greatest risk for high-end
severe would be mid afternoon into the evening. The storms in the
morning could produce severe wind gusts as well, though there is
not that great of a signal for that. SPC has placed most of the
area in an Enhanced Risk for Day2/Wednesday-Wednesday Night.

Another aspect for Wednesday is very heavy rain. PWATs up to 1.8
inches (97th percentile), with slower individual storm motions and
increased covergence combined with such high instability point to
favoring the high-end QPFs (max of HREF) which suggests at least
isolated 4+ inch rainfall amounts could occur if there are repeating
rounds of storms. Uncertainty in how storm evolution occurs precludes
the issuance of a flood watch attm, but will be adding heavy rain
to the forecast to get this messaging out there.

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. In general, probabilities
from models/ensembles for showers gradually diminish while working
through the weekend. We'll have to see if that trend holds up.
Into early next week, chances for rain go down further as high
pressure settles overhead.

Dangerous Heat...Despite the morning storms, temperatures have
already recovered to around 90. Those readings along with super
high dewpoints in the upper 70s to near 80 is already resulting in
apparent temps pushing past 105, with more heating to go during
the day. Though technically we will stay below extreme heat
criteria over central WI, not going to change heat headlines given
how oppressively humid it is and how there was no relief last night.
Also not going to extend the headlines through tomorrow with all
the uncertainty on how storms will impact temperatures on Wednesday.
Will let mid shift assess and re-issue heat headlines for Wednesday
if needed. Beyond Wednesday, unsettled weather and temperatures
not as warm and dewpoints coming down (including into July 4th)
slightly cast doubt on need for additional heat headlines. Upshot
is after the heat today, going to take it day-by-day to see gage
the needs for additional heat headlines.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1247 PM CDT Tue Jun 30 2026

Morning round of storms has exited. Additional storms expected
late this afternoon into this evening. Have kept it simple and
framed out prevailing thunder for a few hours, though it will
likely not be widespread and prevailing as this. Conditions will
be VFR, though like this morning, a direct hit from a TSRA would
result in brief IFR vsby. After a lull late evening through
overnight, another round of storms is expected to arrive over the
entire area on Wednesday morning. Gusty winds could occur with
that round of storms, but will address this with later updates
when confidence increases.

Southwest winds will increase today, with gusts up to 20 kts.
Winds subside late this evening and stay remain less than 10 kts
on Wednesday morning.

&&

.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.....JLA
AVIATION.......JLA

Hazardous Weather Outlook
National Weather Service Green Bay WI
244 PM CDT Tue Jun 30 2026

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-011945-
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-
244 PM CDT Tue Jun 30 2026

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

.DAY ONE...Tonight

Extreme heat warnings and heat advisories will expire at 7 PM this
evening.

Isolated strong to severe thunderstorms are expected 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.

.DAYS TWO THROUGH SEVEN...Wednesday through Tuesday

Daytime heat index values will be near 100 degrees on Wednesday,
especially over east-central WI. A Heat Advisory may be needed.

Thunderstorms are expected Wednesday morning, then again Wednesday
afternoon into Wednesday evening. The storms on Wednesday morning
could produce strong wind gusts. The storms Wednesday afternoon
into Wednesday evening may result in a higher-end severe risk,
with the potential for damaging winds over 70 mph, hail up to
golf-ball sized hail, and an isolated tornado. Heavy rain is
expected Wednesday and Wednesday night, which could produce at
least isolated instances of flash flooding.

Periodic chances for thunderstorms will continue through late this
week. A few storms on Thursday could be strong to severe. Heavy
rain could also occur.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to report peak wind gusts, hail, and any
flooding to the National Weather Service in Green Bay. Spotter
activation may be needed on Wednesday.

LMZ521-522-541>543-011945-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
244 PM CDT Tue Jun 30 2026

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

.DAY ONE...Tonight

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

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

.DAYS TWO THROUGH SEVEN...Wednesday through Tuesday

Periodic chances for thunderstorms will last through the upcoming
weekend. The greatest risk for severe storms will be Wednesday
afternoon into Wednesday evening. Storms occurring Thursday could
be strong to severe. Any thunderstorm would pose a hazard to
mariners.

JLA

Special Weather Statement
National Weather Service Green Bay WI
1109 AM CDT Tue Jun 30 2026

WIZ022-039-040-301700-
Door WI-Brown WI-Kewaunee WI-
1109 AM CDT Tue Jun 30 2026

...AN AREA OF STRONG THUNDERSTORMS WILL IMPACT SOUTHERN DOOR...
KEWAUNEE AND NORTHEASTERN BROWN COUNTIES UNTIL NOON CDT...

At 1109 AM CDT, Doppler radar was tracking an area of strong
thunderstorms over Bellevue Town, or near Green Bay, moving east at
30 mph.

HAZARD...Wind gusts up to 40 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

The strong thunderstorms will be near...
  Bellevue Town around 1110 AM CDT. Luxemburg around 1140 AM CDT.
  Kewaunee around 1155 AM CDT.

Other locations impacted by these strong thunderstorms include
Allouez, Bellevue, Ledgeview, Leo Frigo Bridge, Glenmore,
Ashwaubenon, De Pere, Uw Green Bay, Langes Corners and Bay
Settlement.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4462 8801 4464 8794 4463 8794 4464 8793
      4474 8759 4441 8751 4435 8804 4460 8807
TIME...MOT...LOC 1609Z 253DEG 24KT 4447 8796

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH

JG

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Special Weather Statement
National Weather Service Green Bay WI
405 PM CDT Tue Jun 30 2026

WIZ018-302130-
Lincoln WI-
405 PM CDT Tue Jun 30 2026

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN LINCOLN COUNTY
UNTIL 430 PM CDT...

At 405 PM CDT, Doppler radar was tracking a strong thunderstorm 5
miles south of Dutch Corners, or 14 miles north of Wausau, moving
northeast at 20 mph.

HAZARD...Wind gusts up to 30 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 thunderstorm will be near...
  Merrill around 405 PM CDT. Dutch Corners around 415 PM CDT.

Other locations impacted by this strong thunderstorm include Doering,
Gleason and Bloomville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4512 8970 4513 8974 4532 8953 4525 8943
      4516 8943 4512 8947
TIME...MOT...LOC 2104Z 217DEG 18KT 4516 8956

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...30 MPH

Uhlmann

Special Weather Statement
National Weather Service Green Bay WI
414 PM CDT Tue Jun 30 2026

WIZ019>021-030-031-035>037-074-302215-
Wood WI-Menominee WI-Southern Oconto County WI-Shawano WI-
Northern Oconto County WI-Waupaca WI-Marathon WI-Portage WI-
Langlade WI-
414 PM CDT Tue Jun 30 2026

...AN AREA OF STRONG THUNDERSTORMS WILL IMPACT MENOMINEE...NORTHERN
PORTAGE...NORTHWESTERN WAUPACA...SOUTHEASTERN MARATHON...SOUTHEASTERN
LANGLADE...WESTERN SHAWANO...NORTH CENTRAL WOOD AND NORTHERN OCONTO
COUNTIES UNTIL 515 PM CDT...

At 414 PM CDT, Doppler radar was tracking a cluster of strong
thunderstorms from 10 miles east of Marshfield and northwest Waupaca
County and across eastern Marathon, western Shawano, and western
Menominee counties, moving northeast at 35 mph.

HAZARD...Wind gusts up to 50 mph and penny 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.

Locations impacted include...
  Knowlton, Mosinee, Rothschild, Weston, Bevent, Ringle, Wittenberg,
  Marion, Red River, Neopit, Keshena, Legend Lake, Big Smokey Falls,
  White Lake, Langlade, Gardner Dam Scout Camp, South Branch,
  Mountain and Bear Paw Scout Camp.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4469 8999 4538 8853 4538 8852 4503 8818
      4453 8915 4463 9011
TIME...MOT...LOC 2111Z 239DEG 30KT 4488 8895

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH

MPC