Thunderstorms developed north of a warm front during the afternoon hours on Sunday (5/17). The strongest storms produced hail up to penny size and damaging winds across east-central Wisconsin, causing over $100,000 worth of damage in Two Rivers.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS GRB wrote it up.
Thunderstorms developed north of a warm front during the afternoon hours on Sunday (5/17). The strongest storms produced hail up to penny size and damaging winds across east-central Wisconsin, causing over $100,000 worth of damage in Two Rivers.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Green Bay, WI wrote its last area forecast discussion before the first event at May 17, 1:33 PM CST, 34 minutes earlier. Its key messages:
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
BerschSpecial 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
BerschSpecial 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
BerschPreliminary 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
&&The Green Bay radar (KGRB), 55 km away, was scanning. The volume nearest the first event began at 20:07 UTC.
4 thunderstorm wind, 1 hail. Local standard time, as filed.
Thunderstorm winds produced damage to a barn and flipped a trailer southeast of Chilton. The time of this report is an estimate based on radar data.
Thunderstorm winds damaged a barn near Shoto. The time of this report is an estimate based on radar data.
Thunderstorm winds downed trees west of Two Rivers. The time of this report is an estimate based on radar data.
Penny size hail fell in Appleton.
Thunderstorm winds snapped and uprooted over 100 trees, power lines, and power poles in Two Rivers. 3,500 were without power with over $100,000 worth of damage.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2026Every state in 2026This day in weather historyWarnings in Wisconsin, May 2026
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1325064, 1325065, 1325067, 1325063, 1325066.