Severe Thunderstorm Warning 80, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
222 PM CDT Wed Jul 16 2025

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Heavy rain across portions of central and east-central WI will
  taper off this evening. A Flood Watch is in effect for central
  WI until 7 pm and portions of east-central and northeast WI
  until 10 pm.

- Small risk of severe storms continues through late afternoon across
  central and east-central WI. Damaging winds would be the
  primary risk along with torrential rainfall and possible
  flooding.

- The warm and humid weather will come to an end tonight. Cooler
  and less humid on Thursday and Friday.

- Small craft should exercise caution on the bay of Green Bay through
  late this afternoon. A Small Craft Advisory is in effect for
  the bay and nearshore areas of Lake Michigan tonight into
  Thursday morning.

- An active pattern is expected Friday night through the middle
  of  next week with periodic chances of thunderstorms. Stronger
  storms and heavy rain are possible at times.

&&

.DISCUSSION...
Issued at 219 PM CDT Wed Jul 16 2025

A Mesoscale Convective Vortex continues to move across the region
this afternoon, bringing showers and scattered thunderstorms to
the region. Some of the strongest storms could produce strong
or damaging winds, an isolated tornado and torrential rainfall
across central and east-central WI. This feature will also bring
in additional moisture as precipitable water values at Green Bay
are expected to increase to 2.11 inches late this afternoon or
near the daily record supporting the likelihood of heavy rainfall.
The movement of the mesoscale convective vortex will support a
nearly west to east band of heavy rain across portions of central
into east-central Wisconsin. The greatest rainfall is expected to
fall in a corridor from Marshfield to Wisconsin Rapids to Waupaca
and Wautoma to Appleton and Oshkosh east to Kewaunee and
Manitowoc. For locations south of Highway 29, HREF probabilities
indicated a 50-90% chance of 1 inch of rain, 30-60% chance of 2
inches and a 10-30% chance of 3 inches. The greatest risk of heavy
rain and flooding will continue for the remainder of the
afternoon into early this evening. Rainfall rates in the heavier
showers and storms could be as high as 1 to 3 inches per hour,
resulting in urban street flooding and ponding of water on area
roads while creeks and ditches may rise rapidly. Fishermen and
boaters on rivers should anticipate river rises and faster flows
from runoff Thursday and Friday.

On the backside of the vortex, gusty northerly winds and building
waves will result in hazardous conditions for small craft into
Thursday morning. Also, low stratus is expected tonight, combined
with northerly winds should keep any dense fog away. The big
change will be the cooler weather and much less humid conditions.
Highs on Thursday will only be in the upper 60s to middle 70s. The
dewpoints will continue on Friday and then will increase again
over the weekend.

The westerlies will linger along the U.S./Canadian border through
the rest of the forecast period. This will result in an active
period with periodic chances of showers/storms next week. The
potential exists for stronger storms and heavy rainfall at times.
The first round of storms arrive Friday night into Saturday
morning with dry conditions expected Saturday night into Sunday
night. The chances of showers and storms return Tuesday and
Wednesday. Temperatures will be close to normal this weekend, then
rise above normal for much of next week.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 115 PM CDT Wed Jul 16 2025

An area of showers, with IFR cigs, was located in north-central
WI early this afternoon as isolated showers and storms, with MVFR
cigs, began to develop across central and east-central WI.
Anticipate the area of showers and IFR/LIFR cigs to continue
across north-central WI through this evening, followed by a brief
lull in precip, with additional showers occurring through late
tonight.

The central and east-central WI TAF sites, including KOSH, will
see the greatest risk for thunderstorms this afternoon and evening
as a complex of showers and thunderstorms moves from WSW to ENE.
The thunderstorms will bring heavy downpours causing reduced
vsbys, gusty winds, and MVFR/IFR cigs. Have all of the storms
ending at the central and east-central WI TAF sites around
00-01z Thu, but a few showers may linger for a few hours after
the storms end.

IFR cigs are expected to continue at all TAF sites through early
Thursday morning before slowly lifting and dissipating towards the
end of the TAF period.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 7 PM CDT this evening for WIZ030-031-035>037-
045.

Flood Watch until 10 PM CDT this evening for WIZ038>040-048>050.
&&

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

Hazardous Weather Outlook...UPDATED
National Weather Service Green Bay WI
216 PM CDT Wed Jul 16 2025

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-171930-
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-
216 PM CDT Wed Jul 16 2025

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

.DAY ONE...Tonight

Showers and thunderstorms will continue to move across the
area for the rest of the afternoon into this evening. A few
strong or severe storms are possible through late afternoon,
generally south of Highway 29. Damaging winds and heavy rain will
be the main threats along with flooding. An isolated tornado is
also possible. A Tornado Watch is in effect until 6 pm for
portions of central and east-central WI.

The cluster of showers and storms will also contain locally
heavy rainfall. Some of the stronger storms could produce rainfall
rates of 1 to 3 inches per hour, resulting in localized flooding.
A Flood Watch is in effect into this evening across central and
east-central WI.

.DAYS TWO THROUGH SEVEN...Thursday through Wednesday

There are on and off chances for thunderstorms Friday night
into Saturday and then again towards the middle of next week.
It is too early to determine if or when any severe storms are
possible. Locally heavy rainfall will be possible at times.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to report any flooding or wind damage to
the National Weather Service in Green Bay.

LMZ521-522-541>543-171930-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
216 PM CDT Wed Jul 16 2025

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

.DAY ONE...Tonight

Thunderstorms will pose a significant hazard to mariners for the
rest of the afternoon into this evening. Some of the storms
will produce strong winds and heavy rainfall that could reduce
visibilities below one mile for a brief period of time.

Small craft should exercise caution on the bay for the rest of
the afternoon. A Small Craft Advisory is in effect for the bay
and nearshore areas of Lake Michigan tonight.

.DAYS TWO THROUGH SEVEN...Thursday through Wednesday

A Small Craft Advisory is in effect for the bay and nearshore
areas of Lake Michigan through Thursday morning.

Thunderstorms are possible Saturday, and again at times next week
that would pose a hazard to mariners.

Eckberg