Severe Thunderstorm Warning 40, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
233 PM CDT Sun May 17 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Strong to severe storms and locally heavy rainfall possible at
  times through Monday night. Timing and coverage of severe storms
  still uncertain beyond tonight.

- Drier and cooler weather returns mid to late week. Frost or
  freeze headlines may be needed Tuesday night and Wednesday
  night.

&&

.DISCUSSION...
Issued at 232 PM CDT Sun May 17 2026

Round of strong to severe thunderstorms are main focus through
Monday night. What a difference a day makes. Surface warm front
still to the south and with northeast winds, temps are stuck in
the 40s to lower 50s. Springtime in the Great Lakes. Despite near
stable cold layer, elevated instability into WI has supported
organized storms that are now as close as southern Fox Valley to
the lakeshore. These storms are being forced by MCV that came out
of IA earlier this morning. Based on radar trends and near term
CAMS, expect initial showers/tsra to impact the Fox Valley and
lakeshore areas through late this afternoon (4-5p). Then as 850mb
front lifts north with approaching low-level jet and elevated
instability, could see additional development of showers and
storms through the evening. Lack of MCV/velocity enhancement and
sfc warm sector still well to the south suggests that hail would
be the primary hazard with this activity.

Attention this evening eventually turns to developing cluster of
severe storms along NE/SD border as many CAMS indicate this will
grow upscale and ride eastward, arriving over western WI after
midnight. If this line of storms hold together they would be
supported by increasing low-level shear and could pose a damaging
wind threat as they push into western and north-central cwa overnight.
At the least, wind gusts over 40 mph and heavy downpours can be
expected. As this moves through, sfc warm front will finally be
arriving into our area from the south. If this front is a little
faster moving to the north, would be a better shot at sfc based
severe storms/damaging winds.

Still will ride with working theory supported by good portion of
near term guidance that in wake of the overnight showers and
storms and in a more capped warm sector, there could be a min in
showers and thunderstorms during the day on Monday. Will be warmer
day and the most humid day in a while (dewpoints well into the
60s). Going to have to watch if there is an outflow layed out by
the overnight convection as this could lead to additional
convective initiation (CI). Also, some models still graze
southeast area (OSH, MTW) with round of showers and storms late
morning through early afternoon. Given the extent of instability
that will be present by that time (MLCAPEs up to 2000J/kg), strong
to severe storms could occur. Chance pops cover the scenario on
Monday for now with details to still be resolved.

Primary cold front shifts through late Monday night or even
Tuesday morning. Still hints of pre-frontal sfc trough, waves of
low pressure moving through ahead of the front, perhaps modulated
by upstream convection. Cannot rule out severe storms late Monday
evening or even overnight Monday night as any lift from these
mechanisms will be interacting with MUCAPE of 1500-2500J/kg and
0-1km shear over 30 kts. The stronger low-level shear ahead of the
main cold front could offset the typical downward trend in severe
potential that typically is seen deeper into the night. No qualms
with SPC Day2 slight risk.

Cold front sweeps through Tuesday morning with residual chance of
showers and a few storms. All this comes to an end by Tuesday
afternoon. Tuesday will be a breezy day as southerly winds shift
to the northwest. Temps over eastern WI will remain above normal
with highs in the low to mid 70s. Readings will stay in the 40s
and 50s in Vilas County.

Small chances of showers and storms return late week into the
weekend. Main issue this week will be potential for frost or
freeze headlines Tuesday night and Wednesday night.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 106 PM CDT Sun May 17 2026

Rounds of showers and thunderstorms will continue through late
afternoon over eastern WI. Have continued to outline these with
TEMPO and Prob30 groups. Approaching warm front and cool, moist
northeast flow will result in cigs lowering to IFR and MVFR
through this evening. The warm front may trigger a few more
showers and storms early this evening to its north as it shifts
north. Will then need to watch potential for line of storms
currently developing over NE/SD to sweep in from the west
overnight tonight. Potential for gusty winds to accompany these
storms if they occur.

Rest of the TAF period will feature MVFR cigs over northern WI
and trend to VFR elsewhere in wake of the warm front that lifts
through the area. Some storms could clip lakeshore areas (MTW)
late morning into the early afternoon. Low confidence on that, so
will leave out for now.

&&

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

&&

DISCUSSION.....JLA
AVIATION.......JLA

Hazardous Weather Outlook
National Weather Service Green Bay WI
249 PM CDT Sun May 17 2026

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-182000-
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-
249 PM CDT Sun May 17 2026

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

.DAY ONE...Tonight

An isolated severe storm could occur through late this afternoon
into early this evening, especially from central WI to the lakeshore.
Another potential of severe storms may occur over central and north
central Wisconsin overnight. The primary threat through this evening
will be large hail, gusty winds, and heavy rain. The primary hazard
overnight tonight will be strong to damaging winds and heavy rain.

.DAYS TWO THROUGH SEVEN...Monday through Sunday

The potential for thunderstorms and heavy rainfall will continue
Monday into Tuesday morning. There is a chance of severe storms
with damaging winds and large hail Monday morning through through
Monday evening. The primary hazard with any severe storms overnight
Monday night would be damaging winds. Details and timing remain
uncertain.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed at times tonight.

LMZ521-522-541>543-182000-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
249 PM CDT Sun May 17 2026

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

.DAY ONE...Tonight

There is a chance of thunderstorms. Conditions hazardous to
small craft are expected tonight.

.DAYS TWO THROUGH SEVEN...Monday through Sunday

Conditions hazardous to small craft are expected on the Bay of
Green Bay through Monday evening. Conditions hazardous to small
craft are expected on Lake Michigan through Tuesday evening.

Thunderstorms will be possible from Monday through Tuesday
morning. Any thunderstorm could pose a hazard to mariners.

JLA

Special Weather Statement
National Weather Service Green Bay WI
148 PM CDT Sun May 17 2026

WIZ048-049-171930-
Calumet WI-Winnebago WI-
148 PM CDT Sun May 17 2026

...A STRONG THUNDERSTORM WILL IMPACT CALUMET AND EASTERN WINNEBAGO
COUNTIES THROUGH 230 PM CDT...

At 147 PM CDT, Doppler radar was tracking a strong thunderstorm near
Southern Lake Winnebago, or near North Fond Du Lac, moving northeast
at 30 mph.

HAZARD...Wind gusts up to 40 mph and pea size hail.

SOURCE...Radar indicated.

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

This strong thunderstorm will be near...
  Central Lake Winnebago around 155 PM CDT.
  Northern Lake Winnebago around 215 PM CDT.

Other locations impacted by this storm include Brant, Quinney,
Stockbridge, Eaa, Jericho, Winnebago, Ford Festival Grounds, Black
Wolf Point, Kloten, and Brothertown.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4390 8866 4423 8849 4408 8805 4394 8825
      4394 8840 4389 8840
TIME...MOT...LOC 1847Z 215DEG 24KT 4390 8850

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

Bersch

Special Weather Statement
National Weather Service Green Bay WI
155 PM CDT Sun May 17 2026

WIZ050-171945-
Manitowoc WI-
155 PM CDT Sun May 17 2026

...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN MANITOWOC COUNTY
THROUGH 245 PM CDT...

At 153 PM CDT, Doppler radar was tracking a strong thunderstorm near
Elkhart Lake, or near Plymouth, 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 hail damage to vegetation is
         possible.

This strong thunderstorm will be near...
  Camp Rokilio Scout Camp around 205 PM CDT.
  Cleveland around 220 PM CDT.
  Manitowoc around 235 PM CDT.

Other locations impacted by this storm include Louis Corners, St
Nazianz, Kellners Corners, Clarks Mills, Kiel, Clover, Madsen,
Millhome, School Hill, and Newtonberg.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4395 8804 4418 8776 4408 8759 4390 8769
      4389 8804
TIME...MOT...LOC 1853Z 233DEG 29KT 4381 8806

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

Bersch

Special Weather Statement
National Weather Service Green Bay WI
225 PM CDT Sun May 17 2026

WIZ048-049-172015-
Calumet WI-Winnebago WI-
225 PM CDT Sun May 17 2026

...STRONG THUNDERSTORMS WILL IMPACT CALUMET AND WINNEBAGO COUNTIES
THROUGH 315 PM CDT...

At 224 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Rush Lake to near Oshkosh to near Southern
Lake Winnebago. Movement was northeast at 30 mph.

HAZARD...Wind gusts up to 40 mph and pea size hail.

SOURCE...Radar indicated.

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

Strong thunderstorms will be near...
  Oshkosh and Central Lake Winnebago around 230 PM CDT.
  Northern Lake Winnebago around 245 PM CDT.
  Chilton and High Cliff State Park around 255 PM CDT.
  Menasha around 300 PM CDT.

Other locations impacted by these storms include Killsnake Wildlife
Area, Butte Des Morts, Larsen, Lake Butte Des Morts, Jericho,
Rivermoor, Brothertown, Winneconne, Harbor Springs, and Allenville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4390 8868 4391 8871 4392 8889 4401 8889
      4424 8869 4424 8819 4403 8804 4394 8825
      4394 8840 4389 8840
TIME...MOT...LOC 1924Z 231DEG 27KT 4398 8877 4397 8863 4391 8851

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

Bersch

Preliminary Local Storm Report
National Weather Service Green Bay WI
307 PM CDT Sun May 17 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0245 PM     Rain             1 SSW Plover            44.44N 89.55W
05/17/2026  M1.04 Inch       Portage            WI   Public

&&

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>