Alert archive / Wisconsin / Severe Thunderstorm Warnings in 2026
Severe Thunderstorm Warning 20, NWS Green Bay, WI
NWS Green Bay, WI issued this severe thunderstorm warning at Apr 13, 2026, 7:39 PM CDT for Brown County, Kewaunee County, Wisconsin. It was in force for 51 min. No storm report in the archive falls inside the area while it was in force.
The area
The counties it named.
The facts
- Issued
- Apr 13, 2026, 7:39 PM CDT (00:39 UTC)
- Expired
- Apr 13, 2026, 8:30 PM CDT
- In force
- 51 min
- Issued by
- NWS Green Bay, WI
- Area
- Storm-based polygon
- Hail
- 1.25 in
- Wind
- 60.0 mph
Counties Brown County, WI, Kewaunee County, WI
The radar
The Green Bay radar (KGRB), 28 km from the middle of the area, began a volume at 00:41 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The nearest sounding before it
Davenport, (KDVN), launched 00:00Z, 0.7 hours before the alert went out and 388 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 1474 J/kg
- Mixed-layer CIN
- -122 J/kg
- Mixed-layer LCL
- 1240 m above ground
- 0-6 km bulk shear
- 32 kt
- 0-1 km storm-relative helicity
- 246 m²/s²
- 0-3 km storm-relative helicity
- 387 m²/s²
- Significant tornado parameter
- 0.8
- Supercell composite
- 19.3
What forecasters said that day
The local office's own words before this severe thunderstorm warning went out, 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 this severe thunderstorm warning went out at Apr 13, 2:44 PM CDT, 4 hours 55 minutes earlier. Its key messages:
- Thunderstorms will develop late this afternoon and continue into the overnight hours with hail in excess of 2 inches, damaging winds and a tornado possible with the strongest storms. The highest risk is across central Wisconsin.
- Rainfall amounts of 1 to 3 inches across parts of central into east-central Wisconsin may lead to additional flood concerns through tonight.
- An active stretch of weather continues through late week with continued periods of showers and storms. The risk area for severe storms shifts south on Tuesday, but extends north into parts of central and east-central Wisconsin.
- Minor to moderate river flooding is ongoing or forecast to occur on several area rivers. Expect many rivers to rise this week due to additional rain and runoff from Upper Michigan, with the greatest impacts expected on the Menominee River, where some locations may see major flooding during the mid to late part of the week.
Area forecast discussion, Apr 13, 2:44 PM CDT, 4 hours 55 minutes before
Area Forecast Discussion
National Weather Service Green Bay WI
244 PM CDT Mon Apr 13 2026
.KEY MESSAGES...
- Thunderstorms will develop late this afternoon and continue
into the overnight hours with hail in excess of 2 inches,
damaging winds and a tornado possible with the strongest
storms. The highest risk is across central Wisconsin.
- Rainfall amounts of 1 to 3 inches across parts of central into
east-central Wisconsin may lead to additional flood concerns
through tonight.
- An active stretch of weather continues through late week with
continued periods of showers and storms. The risk area for
severe storms shifts south on Tuesday, but extends north into
parts of central and east-central Wisconsin.
- Minor to moderate river flooding is ongoing or forecast to
occur on several area rivers. Expect many rivers to rise this
week due to additional rain and runoff from Upper Michigan,
with the greatest impacts expected on the Menominee River,
where some locations may see major flooding during the mid to
late part of the week.
&&
.DISCUSSION...
Issued at 245 PM CDT Mon Apr 13 2026
Tonight: Severe Storms/Heavy Rain
Early afternoon surface analysis indicated a surface low over
central Nebraska with a warm front snaking eastward across
northern Iowa into central Wisconsin. MLCAPE has increased to
around 1000 J/kg across central Wisconsin with some inhibition
noted.
Late this afternoon, expect more focused storm
initiation/intensification generally in the vicinity of the
warm front and nose of the low- level jet. Surface-based
instability is maximized over central Wisconsin (1000-2000 J/kg)
by late this afternoon with effective shear around 40-50 kts.
Combined with steep lapse rates already sampled by the 18Z GRB
RAOB, the environment will be supportive of large to very large
hail. The tornado risk likely will be highest along the warm
front from west-central Wisconsin into perhaps central
Wisconsin as the low-level jet increases early this evening and
overlaps the warm front/instability axis. Damaging wind risk
will depend on the degree of upscale growth/organization of
storms. Overall, the severe weather risk lessens with northward
extent.
Precipitable water values remain near the top of climatology for
mid April. HREF probability matched mean 24-hr rainfall is in
the 1 to 3 inch range across parts of central into east-central
Wisconsin through tonight, on the nose of the low-level jet.
However, rainfall amounts will depend on the organization and
degree of training. This rainfall could exacerbate already
saturated soils.
Areas of fog may also develop overnight behind the storms.
Tuesday: Additional storms
The front slides south on Tuesday with the instability axis also
displaced south. The placement of the boundary will impact the
northward extent of severe weather during the
afternoon/evening. RAP hodographs show lesser low-level shear
although an elongated profile favorable for large hail and
winds. Currently the highest risk of severe storms is across
southern Wisconsin, but could extend into parts of east-central
Wisconsin.
Wednesday-Monday: Active into the weekend
Southwest flow aloft persists into late week keeping the area in
a warm, wet pattern. Another shortwave trough will bring
additional shower (40-80%) chances Wednesday into Thursday. A
more dynamic trough is slated to impact the region late Friday
into the weekend bringing additional widespread rainfall and
storms. The northward extent of greater instability is somewhat
uncertain with this system, impacting severe weather potential,
but this will be something to watch in the coming days. Drier
and cooler weather is expected behind this system for early next
week.
&&
.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1251 PM CDT Mon Apr 13 2026
Widespread showers and storms will develop late this afternoon
into the overnight hours with MFVR/IFR conditions. Initial
storms may begin to initiate by 21-22Z today, becoming more
widespread this evening. Areas of fog/low clouds will likely
persist into Tuesday.
&&
.HYDROLOGY...
Issued at 245 PM CDT Mon Apr 13 2026
Flooding is expected to continue on several area rivers during
the week, and will be exacerbated by periodic heavy rainfall.
Runoff from Upper Michigan is still expected to bring moderate
to major flooding along the Menominee River, especially during
the mid to late part of the week. If you live near a river or
stream, keep a close eye on water levels this week and monitor
the latest Flood Warnings from the National Weather Service in
Green Bay.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch through Tuesday morning for WIZ013-018>022-030-031-
035>040-045-048>050-073-074.
MARINE...None.
&&
DISCUSSION...JM
AVIATION...JM
HYDROLOGY...Kieckbusch/JMHazardous weather outlook, Apr 13, 2:51 PM CDT, 4 hours 48 minutes before
Hazardous Weather Outlook National Weather Service Green Bay WI 251 PM CDT Mon Apr 13 2026 WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-142000- 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- 251 PM CDT Mon Apr 13 2026 This Hazardous Weather Outlook is for north-central and northeast Wisconsin. .DAY ONE...Tonight Elevated water levels or flooding continue along some rivers. Severe storms, including heavy rainfall, large to very large hail, damaging winds and tornado or two are possible late this afternoon into tonight. The highest risk of severe storms is across central into east- central Wisconsin. Additional flooding may occur for areas that receive heavy rainfall tonight. .DAYS TWO THROUGH SEVEN...Tuesday through Monday There is a chance of severe thunderstorms south of a line from Wisconsin Rapids to Sturgeon bay during the late afternoon and evening on Tuesday. Large hail and strong winds will be the primary threats. Additional thunderstorms are possible Wednesday afternoon into Wednesday night, and again Friday night into Saturday. Elevated water levels and at least minor flooding will continue along many rivers through the week. Runoff from the Upper Peninsula will likely result in moderate to possibly major flooding on the Menominee River during the mid to late part of the week. .SPOTTER INFORMATION STATEMENT... Spotters should report severe weather and flooding to the National Weather Service in Green Bay. LMZ521-522-541>543-142000- The Bay of Green Bay south of a line from Cedar River MI to Rock Island Passage-Lake Michigan from Washington Island to Sheboygan- 251 PM CDT Mon Apr 13 2026 This Hazardous Weather Outlook is for portions of northwest Lake Michigan and the waters of Green Bay. .DAY ONE...Tonight Thunderstorms, some possibly strong to severe, are expected tonight. Areas of fog are possible. .DAYS TWO THROUGH SEVEN...Tuesday through Monday Thunderstorms will be possible at times Tuesday through Wednesday night, and again Friday night into Saturday. Severe storms will be possible Tuesday evening.
In the hours before
Local storm report, Apr 13, 6:41 PM CDT, 58 minutes before
Preliminary Local Storm Report
National Weather Service Green Bay WI
641 PM CDT Mon Apr 13 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0608 PM Hail 5 NE Marshfield 44.71N 90.10W
04/13/2026 E1.25 Inch Marathon WI Public
&&Local storm report, Apr 13, 7:09 PM CDT, 30 minutes before
Preliminary Local Storm Report
National Weather Service Green Bay WI
709 PM CDT Mon Apr 13 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0637 PM Hail 2 ESE Peru 44.55N 89.20W
04/13/2026 M1.25 Inch Waupaca WI Amateur Radio
&&Local storm report, Apr 13, 7:26 PM CDT, 13 minutes before
Preliminary Local Storm Report
National Weather Service Green Bay WI
726 PM CDT Mon Apr 13 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0714 PM Hail Clintonville 44.61N 88.75W
04/13/2026 M0.50 Inch Waupaca WI Trained Spotter
&&Special weather statement, Apr 13, 7:30 PM CDT, 9 minutes before
Special Weather Statement
National Weather Service Green Bay WI
730 PM CDT Mon Apr 13 2026
WIZ039-074-140100-
Southern Oconto County WI-Brown WI-
730 PM CDT Mon Apr 13 2026
...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN BROWN AND SOUTHERN
OCONTO COUNTIES THROUGH 800 PM CDT...
At 730 PM CDT, Doppler radar was tracking a strong thunderstorm near
Green Bay, moving northeast at 45 mph.
HAZARD...Wind gusts up to 40 mph and half inch 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...
Green Bay around 735 PM CDT.
Other locations impacted by this storm include Anston, Stiles,
Sobieski, Kunesh, South Chase, Pensaukee, Lambeau Field, Chase,
Hobart, and Leo Frigo Bridge.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
A Tornado Watch remains in effect until 1000 PM CDT for northeastern
Wisconsin.
&&
LAT...LON 4447 8819 4459 8819 4459 8824 4496 8811
4487 8777 4486 8777 4471 8792 4463 8793
4467 8783 4442 8804
TIME...MOT...LOC 0030Z 205DEG 39KT 4453 8811
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH
KScharfSpecial weather statement, Apr 13, 7:36 PM CDT, 3 minutes before
Special Weather Statement
National Weather Service Green Bay WI
736 PM CDT Mon Apr 13 2026
WIZ031-036-037-140100-
Waupaca WI-Shawano WI-Portage WI-
736 PM CDT Mon Apr 13 2026
...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN PORTAGE...
NORTHWESTERN WAUPACA AND WESTERN SHAWANO COUNTIES THROUGH 800 PM
CDT...
At 736 PM CDT, Doppler radar was tracking a strong thunderstorm 10
miles southeast of Bevent, or 18 miles northeast of Stevens Point,
moving east at 40 mph.
HAZARD...Wind gusts of 50 to 55 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.
Locations impacted include...
Stevens Point, Whiting, Plover, Stockton, Marion, Pella, Tigerton,
Jordan, Rosholt, and Bowler.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
A Tornado Watch remains in effect until 1000 PM CDT for central and
northeastern Wisconsin.
&&
LAT...LON 4464 8951 4468 8942 4468 8923 4478 8922
4491 8896 4476 8875 4457 8884 4448 8954
TIME...MOT...LOC 0036Z 250DEG 34KT 4465 8923
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...55 MPH
KScharfLocal storm report, Apr 13, 7:38 PM CDT, 1 minute before
Preliminary Local Storm Report
National Weather Service Green Bay WI
738 PM CDT Mon Apr 13 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0729 PM Hail 2 WNW Ashwaubenon 44.50N 88.11W
04/13/2026 M0.50 Inch Brown WI NWS Employee
0734 PM Hail 2 W Howard 44.56N 88.09W
04/13/2026 M0.50 Inch Brown WI Public
&&The office that day
Everything else NWS Green Bay, WI issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 13, 7:02 PM CDT | Areal Flood Advisory | GRB | Outagamie, Shawano, Waupaca | 3 hr |
| Apr 13, 7:19 PM CDT | Severe Thunderstorm Warning | GRB | Lincoln, Marathon | 14 min |
| Apr 13, 7:22 PM CDT | Severe Thunderstorm Warning | GRB | Outagamie, Shawano, Waupaca | 38 min |
| Apr 13, 7:30 PM CDT | Special Weather Statement | GRB | Brown | 30 min |
| Apr 13, 7:31 PM CDT | Special Marine Warning | GRB | 89 min | |
| Apr 13, 7:36 PM CDT | Special Weather Statement | GRB | Waupaca | 24 min |
| Apr 13, 7:41 PM CDT | Severe Thunderstorm Warning | GRB | Portage, Shawano, Waupaca | 49 min |
| Apr 13, 7:57 PM CDT | Special Marine Warning | GRB | 2 hr | |
| Apr 13, 7:58 PM CDT | Severe Thunderstorm Warning | GRB | Wood | 47 min |
| Apr 13, 8:06 PM CDT | Flash Flood Warning | GRB | Marathon, Outagamie, Portage, Shawano, Waupaca | 8 hr |
| Apr 13, 8:22 PM CDT | Severe Thunderstorm Warning | GRB | Brown, Kewaunee, Manitowoc | 42 min |
| Apr 13, 8:36 PM CDT | Areal Flood Advisory | GRB | Brown, Oconto, Outagamie | 3 hr |
| Apr 13, 8:36 PM CDT | Severe Thunderstorm Warning | GRB | Portage, Wood | 35 min |
| Apr 13, 9:10 PM CDT | Severe Thunderstorm Warning | GRB | Portage, Waushara, Wood | 50 min |
| Apr 13, 9:26 PM CDT | Special Weather Statement | GRB | Brown | 34 min |
| Apr 13, 9:30 PM CDT | River Flood Warning | GRB | Waupaca | 5 days |
| Apr 13, 9:32 PM CDT | River Flood Warning | GRB | Wood | 63 hr |
| Apr 13, 9:56 PM CDT | Special Weather Statement | GRB | Waupaca | 34 min |
| Apr 13, 10:01 PM CDT | Flash Flood Warning | GRB | Brown, Door, Kewaunee, Oconto, Outagamie | 6 hr |
| Apr 13, 10:16 PM CDT | River Flood Warning | GRB | Wood | 70 hr |
| Apr 13, 10:21 PM CDT | Areal Flood Advisory | GRB | Brown, Calumet, Kewaunee, Manitowoc, Outagamie, Portage and 4 more | 6 hr |
| Apr 13, 10:35 PM CDT | Special Weather Statement | GRB | Brown, Calumet, Outagamie, Winnebago | 55 min |
| Apr 13, 10:54 PM CDT | Flash Flood Warning | GRB | Brown, Calumet, Kewaunee, Manitowoc, Outagamie, Winnebago | 5 hr |
| Apr 13, 11:27 PM CDT | Special Weather Statement | GRB | Calumet, Manitowoc | 33 min |
| Apr 14, 2:14 AM CDT | Flash Flood Watch | GRB | Waupaca | 3 hr |
| Apr 14, 2:40 AM CDT | River Flood Warning | GRB | Brown | 21 days |
| Apr 14, 3:52 AM CDT | Areal Flood Advisory | GRB | Brown, Calumet, Door, Kewaunee, Manitowoc, Marathon and 6 more | 6 hr |
| Apr 14, 4:57 AM CDT | River Flood Warning | GRB | Marinette | 6 days |
| Apr 14, 6:02 AM CDT | Areal Flood Warning | GRB | Outagamie, Shawano, Waupaca | 5 hr |
| Apr 14, 8:46 AM CDT | Flash Flood Watch | GRB | Shawano, Waupaca | 25 hr |
| Apr 14, 9:07 AM CDT | River Flood Warning | GRB | Wood | 21 days |
| Apr 14, 9:08 AM CDT | River Flood Warning | GRB | Manitowoc | 21 days |
| Apr 14, 9:43 AM CDT | Areal Flood Warning | GRB | Brown, Door, Kewaunee, Oconto, Outagamie, Shawano and 1 more | 9 hr |
| Apr 14, 9:48 AM CDT | Areal Flood Warning | GRB | Brown, Calumet, Kewaunee, Manitowoc, Outagamie | 9 hr |
| Apr 14, 10:16 AM CDT | Flash Flood Warning | GRB | Waupaca | 6 hr |
| Apr 14, 11:23 AM CDT | River Flood Warning | GRB | Marathon | 34 hr |
| Apr 14, 2:09 PM CDT | River Flood Warning | GRB | Kewaunee | 32 hr |
| Apr 14, 4:37 PM CDT | River Flood Warning | GRB | Brown, Outagamie | 44 hr |
| Apr 14, 5:53 PM CDT | Severe Thunderstorm Warning | GRB | Wood | 37 min |
| Apr 14, 6:10 PM CDT | Severe Thunderstorm Warning | GRB | Waushara, Winnebago | 50 min |
| Apr 14, 6:33 PM CDT | Special Weather Statement | GRB | Portage, Wood | 27 min |
| Apr 14, 6:46 PM CDT | Areal Flood Advisory | GRB | Portage, Wood | 2 hr |
| Apr 14, 6:51 PM CDT | Areal Flood Warning | GRB | Brown, Door, Kewaunee, Oconto, Outagamie, Shawano and 1 more | 9 hr |
| Apr 14, 6:53 PM CDT | Areal Flood Warning | GRB | Brown, Calumet, Kewaunee, Manitowoc, Outagamie | 9 hr |
Nearby
Severe Thunderstorm Warnings in Wisconsin, 2026Every severe thunderstorm warning in 2026
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.