June 22, 2024 Southern Wisconsin Tornado Outbreak
9 tornadoes touch down during the evening hours across southern Wisconsin.
Overview
Event By The Numbers
2
Diameter, in inches, of the largest hail stone reported during the June 22 event. Approximately the size of an egg, the hail stone fell near the community of Maple Bluff in Dane County.
3
Number of particularly dangerous situation (PDS) tornado warnings issued by NWS Milwaukee/Sullivan during the event. The June 22, 2024 outbreak marked only the second time that NWS Milwaukee/Sullivan issued a PDS tornado warning, with the first being during the historic February 8, 2024 tornado event. PDS tornado warnings are reserved for rare situations when large tornadoes are confirmed to be on the ground and causing significant damage.
5
Total number of flash flood warnings issued by NWS Milwaukee/Sullivan. A hazard that can often be overlooked by the public during severe weather, multiple reports of flash flooding were received from Dane, Columbia, and Sauk Counties during the June 22 event.
28
Total number of severe weather warnings issued by NWS Milwaukee/Sullivan during the event. 11 tornado warnings (red polygons) and 17 severe thunderstorm warnings (yellow polygons) made up this total.
36
Total number of storm reports – including the 9 tornadoes (cyan, lime green, and yellow lines) – received by NWS Milwaukee/Sullivan during the June 22 outbreak. 18 straight-line wind reports (blue squares) and 9 large hail reports (green circles) contributed to this total.
135
Highest estimated tornadic wind gust of the event, in miles per hour. The gusts occurred at the Apple Grove Church along the Argyle tornado path.
700
Maximum width, in yards, of the Janesville tornado. Just shy of four-tenths of a mile wide, the Janesville tornado was the widest of the June 22 outbreak.
The Tornadoes
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The Meteorology
Synoptic Environment
The upper level pattern was marked by enhanced, west-southwesterly flow across the northern United States on June 22. Southern Wisconsin would remain beneath said enhanced upper level flow throughout the entirety of the day on June 22. Several pockets of divergence—areas where wind spreads out in different directions—were apparent within the jet of west-southwest winds, creating an environment favorable for upward motions in the low to middle portions of the atmosphere. These upward motions encourage the development of low pressure systems at the surface, in addition to supporting shower and thunderstorm development in the presence of sufficient moisture and instability.
In the middle levels of the atmosphere, a train of shortwave troughs tracked from the Northern Plains through the Western Great Lakes on June 22. The first would cross the state from morning through early afternoon, with a second approaching during the afternoon and evening hours. Similar to areas of divergence in the upper portions of the atmosphere, shortwave troughs encourage rising motions throughout the low to middle portions of the atmosphere. Said motions provide additional support for low pressure development at the surface, as well as shower and thunderstorm formation if enough moisture and instability are present.
Tied to the leading shortwave trough crossing the state during the morning hours, an area of low pressure was situated across northeastern Wisconsin throughout the day on June 22. A cold front branched out and to the southwest of the low, moving slowly southeast through early afternoon. Affiliated with divergence embedded within the west-southwesterly upper jet, a second area of low pressure formed along the Minnesota-Iowa border during the mid-afternoon hours, tracking along the surface front as it moved into southern Wisconsin. The formation and subsequent track of this second surface low across southern Wisconsin likely played a critical role in the development of tornadoes on the afternoon of June 22. The crucial role of the second surface low is explored further in the mesoscale section below.
Mesoscale Environment
Building along and south of the surface front, a muggy and unstable air mass had built into south-central and southwestern Wisconsin by mid-afternoon on June 22. Characterized by mixed layer CAPE (MLCAPE) values between 1000-1500 joules per kilogram, as well as precipitable water values approaching and exceeding two inches, said air mass was quickly becoming primed for thunderstorms capable of producing heavy rain.
Thanks to enhanced southwest winds aloft, effective bulk shear values between 30 and 45 knots overlapped with this primed air mass. Organized, potentially severe, thunderstorms were thus becoming favored as well.
Whether or not organized storms would produce tornadoes remained less certain, however, given only modest storm relative helicity (SRH) values between 100-150 m2/s2 in place across the region.
The question of tornado potential was likely settled by the development of the secondary surface low in along the Iowa-Minnesota border. Tracking into southwestern and south-central Wisconsin during the late afternoon and evening hours, southerly winds immediately ahead of the low pressure center helped to pull even greater amounts of instability into the regions impacted by tornadoes.
Further, the orientation of the southerly winds acted to increase directional wind shear, and thus SRH values, as thunderstorms tracked across southwestern and south-central Wisconsin.
Said increases in SRH, along with the minor boosts in instability, enhanced the potential for supercells and possibly significant (EF2+) tornadoes across southwestern and south-central Wisconsin.
Event Timeline
2:00 AM June 20 - 5:00 AM June 22: Confidence in all-hazards severe weather on June 22 begins to increase, but with several caveats. A pair of surface fronts, an approaching upper disturbance, sufficient wind shear, and a very humid air mass will create an environment favorable for severe thunderstorms on the afternoon of June 22. Whether or not this potential will materialize will depend on early day cloud cover and rainfall on the morning of the 22nd, which would act to stabilize an otherwise primed environment for severe thunderstorms.
2:16 AM June 20
The Storm Prediction Center inserts a slight (level 2/5) risk for severe thunderstorms over north-central and southwestern Wisconsin in its June 22 severe weather outlook. A marginal (level 1/5) risk is inserted across southeastern portions of the state. Severe weather potential will depend on early day showers and storms, as well as precise placement of surface fronts across the region. Models disagree on the timing and placement of the aforementioned features, making future changes to the outlook areas likely. In the event severe storms develop, all hazards will be possible.
5:10 AM June 20
NWS Milwaukee/Sullivan begins to message increasing severe weather concerns on June 22 in its area forecast discussion.
3:15 PM June 20
NWS Milwaukee/Sullivan begins to message June 22 severe weather potential on social media and to core partners. All severe weather hazards remain possible, though how far southeast severe storms will reach remains unclear.
1:00 AM June 21
The Storm Prediction Center continues to carry a slight (level 2/5) severe thunderstorm risk in its June 22 severe weather outlook. The level 2/5 risk area is shifted southeast given latest model trends on front placements, and now includes the majority of southern Wisconsin. All severe weather hazards remain possible.
5:00 AM June 21
NWS Milwaukee/Sullivan releases an updated June 22 severe weather graphicast on social media and to core partners. All severe weather hazards are possible during a relatively broad window of severe weather potential. Whether or not storms survive to the Lake Michigan shoreline remains unclear.
12:55 AM June 22
The Storm Prediction Center shifts the slight (level 2/5) severe weather risk even further southeast in its updated June 22 severe weather outlook, with the risk area now including all of southern Wisconsin. The southeast shift aligns with the most likely area of afternoon destabilization behind early day showers and storms. How many strong to severe storms will develop remains unclear, thanks to the aforementioned early day rainfall.
4:30 AM June 22
NWS Milwaukee/Sullivan issues an updated June 22 severe weather graphicast. If early day showers and storms can push out fast enough, a broad window of severe weather potential will exist during the afternoon hours. All severe weather hazards, in addition to heavy rainfall and flash flooding, will be possible should this potential be realized.
Milwaukee, WI (KMKX) radar imagery between 1 PM & 3 PM (18 & 20Z) June 22. Mixed layer CAPE (MLCAPE) is overlaid with radar imagery.
12:00 - 9:30 PM June 22: The forecast picture clarifies, as early day rain showers push east and conditions destabilize over southwestern Wisconsin. Scattered to numerous showers and storms develop, resulting in nine confirmed tornadoes, and multiple reports of large hail and damaging winds.
12:56 PM June 22
The Storm Prediction Center issues Mesoscale Discussion 1372 for portions of south-central and southwestern Wisconsin. The discussion highlights increasing potential for strong to severe storms along and south of the warm front as a shortwave trough moves in from the west. All hazards—including tornadoes—will be possible in this activity.
2:18 PM June 22
With a shortwave trough quickly approaching from the west, and two surface fronts on a collision course, NWS Milwaukee/Sullivan continues to highlight increasing severe weather potential across southern Wisconsin
3:15 PM June 22
Tornado Watch 446 is issued for areas along and west of Interstate 39. The watch is later extended east into Ozaukee, Milwaukee, Kenosha, and Racine Counties.
4:02 PM June 22
With thunderstorm development in-progress across northeastern Iowa and along the warm-cold front intersection in southwest Wisconsin, NWS Milwaukee/Sullivan messages a now imminent severe weather threat over southwestern and south-central Wisconsin
5:15 PM June 22
NWS La Crosse issues a tornado warning – the first severe warning of the afternoon – for southern portions of Grant County as a rotating supercell crosses the Mississippi River from Iowa.
5:25 PM June 22
The Storm Prediction Center issues Mesoscale Discussion 1377 for portions of south-central and southwestern Wisconsin. The discussion highlights a corridor of greater near-term potential over portions of Grant, Iowa, and Lafayette Counties.
5:37 PM June 22
The Cornelia tornado touches down in eastern Grant County, tracking along a brief 0.2 mile path over the next minute.
5:40 - 6:00 PM June 22
The supercell responsible for the Cornelia tornado approaches Lafayette County from the west. Severe thunderstorm and tornado warnings are also issued for a bowing cluster of storms along the Wisconsin River.
6:02 PM June 22
The Belmont tornado touches down in Lafayette County. The tornado remains on the ground for the next ten minutes, tracking just over five and a half miles.
6:10 - 6:30 PM June 22
The Lafayette County supercell continues to push east. Severe storms enter the northern Madison metro from the Wisconsin Valley, with additional severe storms moving into Iowa County.
6:36 PM June 22
The Argyle tornado touches down in Lafayette County. The tornado remains on the ground for the next twelve minutes, tracking nearly seven miles.
6:41 PM June 22
With reports of significant damage being received along the Argyle tornado path, NWS Milwaukee/Sullivan upgrades the ongoing tornado warning for eastern Lafayette and western Green Counties to a PDS tornado warning.
6:45 - 7:00 PM June 22
The supercell responsible for the Argyle tornado moves into western Green County. Storms take on a more supercellular appearance over northeastern Dane County, with multiple large hail reports arriving from the communities of Maple Bluff and Sun Prairie. Additional severe storms move into the southwestern Madison metro from Iowa County.
7:10 PM June 22
The Marshall tornado touches down in eastern Dane County. The tornado remains on the ground for five minutes, tracking four and half miles into western Jefferson County.
7:14 PM June 22
With ground confirmations of a large tornado on the ground near Marshall, NWS Milwaukee/Sullivan upgrades the ongoing tornado warning for northeastern Dane, southwestern Dodge, and northwestern Jefferson Counties to a PDS tornado warning.
7:29 PM June 22
The Storm Prediction Center issues Mesoscale Discussion 1380 for south-central and southeastern Wisconsin. The discussion highlights that tornado potential will continue east toward Lake Michigan through the remainder of the evening.
7:30 PM June 22
The Watertown tornado touches down in northern Jefferson County. The tornado remains on the ground for the next five minutes, tracking just over two miles to the northeast.
7:42 PM June 22
The Janesville tornado touches down to the west of the Southern Wisconsin Regional Airport in Rock County. The tornado tracks just over six miles east-northeast over the next eleven minutes.
7:51 PM June 22
The Janesville tornado crosses Interstate 39 at Avalon Road, just to the southeast of downtown Janesville. Traffic cameras from the Wisconsin DOT capture the crossing.
7:52 PM June 22
Trained spotters confirm that the Janesville tornado is producing damage, and has grown large in size. The ongoing tornado warning for Rock County is upgraded to a PDS tornado warning.
7:55 - 8:15 PM June 22
Consolidating into a single, organized line, severe thunderstorms push east toward Lake Michigan. Severe thunderstorm and tornado warnings continue.
8:22 PM June 22
The Williams Bay tornado touches down near Delavan Lake in Walworth County. The tornado moves southeast along a six mile path over the next eight minutes. The Fontana tornado simultaneously touches down near the south shore of Geneva Lake, tracking just over five miles to the northeast over the next seven minutes.
8:42 PM June 22
The final tornado of the outbreak touches down just east of Powers Lake in Kenosha County. The tornado remains on the ground for a brief two minutes, tracking nearly a mile and half to the east.
8:45 - 9:20 PM June 22
Strong to severe storms push south and east into northern Illinois and Lake Michigan. All severe warnings end across southern Wisconsin.
Damage Photos
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1
Barn Damage Along The Belmont Tornado Path
Estimated wind speeds of 85 MPH
2
Tree & Structural Damage Along The Argyle Tornado Path
Estimated wind speeds of 100 MPH
3
Storage Shed Swept Away Along The Argyle Tornado Path
Estimated wind speeds of 120 MPH
4
Tree Damage Near The Apple Grove Community Church (Lafayette County)
Estimated wind speeds between 130 and 135 MPH
5
Damage At The Apple Grove Church Along The Argyle Tornado Path
Estimated wind speeds of 135 MPH
6
Destroyed Outbuilding Along The Argyle Tornado Path
Estimated wind speeds of 110 MPH
7
Damage To A Snowmobile Storage Shed Along The Argyle Tornado Path
Estimated wind speeds of 90 MPH
8
Barn & Silo Damage Along The Argyle Tornado Path
Estimated wind speeds of 95 MPH
9
Destroyed Outbuilding Along The Argyle Tornado Path
Estimated wind speeds of 95 MPH
10
Tree Damage Along The Argyle Tornado Path
Estimated wind speeds of 90 MPH
11
Tree Damage At The Beginning Of The Janesville Tornado Path
Estimated wind speeds of 90 MPH
12
Roof Damage Along The Janesville Tornado Path
Estimated wind speeds of 105 MPH
13
Sawed Off Trees Along The Janesville Tornado Path
Estimated wind speeds of 115 MPH
14
Flattened Grove Of Trees Along The Janesville Tornado Path
Estimated wind speeds of 115 MPH
15
Garage Damage Along The Janesville Tornado Path
Estimated wind speeds of 110 MPH
16
House Missing Its Roof Along The Janesville Tornado Path
Estimated wind speeds of 110 MPH
17
Garage Damage Along The Janesville Tornado Path
Estimated wind speeds of 105 MPH
18
House Damage Along The Janesville Tornado Path
Estimated wind speeds of 110 MPH
19
Warehouse Damage Along The Janesville Tornado Path
Estimated wind speeds of 110 MPH
20
Destroyed Outbuilding Along The Janesville Tornado Path
Estimated wind speeds of 100 MPH
21
Roof Damage Along The Janesville Tornado Path
Estimated wind speeds of 110 MPH
22
Garage Damage Along The Janesville Tornado Path
Estimated wind speeds of 105 MPH
23
Garage Damage Along The Janesville Tornado Path
Estimated wind speeds of 110 MPH
24
House Damage Along The Janesville Tornado Path
Estimated wind speeds of 115 MPH
25
Debris Scatter Along The Janesville Tornado Path
Estimated wind speeds of 115 MPH
26
Tree On A Roof Along The Janesville Tornado Path
Estimated wind speeds between 105 and 110 MPH
27
Warehouse Damage Along The Janesville Tornado Path
Estimated wind speeds of 105 MPH
28
Toppled Light Pole Near The End Of The Janesville Tornado Path
Estimated wind speeds of 100 MPH
29
Tree Damage Near The End Of The Janesville Tornado Path
Estimated wind speeds of 100 MPH
30
Roof Damage Along The Williams Bay Tornado Path
Estimated wind speeds of 85 MPH
31
House Damage Along The Williams Bay Tornado Path
Estimated wind speeds of 100 MPH
32
House Damage Along The Williams Bay Tornado Path
Estimated wind speeds of 100 MPH
33
House Damage Along The Williams Bay Tornado Path
Estimated wind speeds of 100 MPH
34
Siding And Window Damage Along The Williams Bay Tornado Path
Estimated wind speeds of 80 MPH
35
House Damage Along The Williams Bay Tornado Path
Estimated wind speeds of 105 MPH
36
Tree Damage Along The Williams Bay Tornado Path
Estimated wind speeds of 90 MPH
37
Tree Damage Along The Williams Bay Tornado Path
Estimated wind speeds of 90 MPH
38
Boat Dock Damage Along The Fontana Tornado Path
Estimated wind speeds of 100 MPH
39
Snapped Trees Along The Fontana Tornado Path
Estimated wind speeds of 100 MPH
40
Shed Blown Off Its Foundation Along The Fontana Tornado Path
Estimated wind speeds of 90 MPH
41
Toppled Trees Along The Fontana Tornado Path
Estimated wind speeds of 90 MPH
42
Downed Tree & Garage Damage Along The Fontana Tornado Path
Estimated wind speeds of 90 MPH
