Several supercell thunderstorms developed along a very strong warm front and produced nine tornadoes from Akaska to Bowdle to Hecla. The largest of the tornadoes was an EF4 tornado which occurred near Bowdle. This tornado produced devastating damage in the Bowdle area. The other tornadoes ranged from EF0 to EF2 and caused extensive tree and building damage.  Nearly one-hundred power poles were downed along with several high line towers leaving nearly a thousand customers without power. Also, very strong straight line winds and large hail up to the size of golfballs affected parts of the area causing some damage.

Tornado in EDMUNDS, SOUTH DAKOTA
From 22-MAY-10 17:29:00 to 22-MAY-10 17:40:00 (CST-6)
Location: BOWDLE
Tornado F-scale: EF4
Reported by: NWS Storm Survey

An EF2 tornado in eastern Walworth county crossed into western Edmunds county and intensified into a large EF4 tornado as it struck several farms in its path. At the first farm, several large cottonwood trees were uprooted along with damage to several trailers. Three grain bins were also destroyed with debris located several hundred yards to the northeast. The residence suffered some shingle and antenna damage. The tornado then tracked northeast to a second farm where several outbuildings were damaged or destroyed along with widespread tree damage. The main residence at this location suffered no damage. Several grain cars were also rolled about 100 yards into the trees behind the house.
The large tornado continued to track northeast to a third farm to the north of Bowdle. The main residence suffered major damage to walls with part of the roof structure removed. Widespread tree damage was sustained with many of the
trees completely debarked with only the stumps of the largest branches
remaining. Two large garages were completely destroyed with the
concrete slab wiped clean. The vehicles in one garage were
rolled or tossed from 25 to 100 yards away. It is estimated that one
vehicle flew through the air 75 to 100 yards resting in the tree
shelter belt to the north of the residence. Several other outbuildings were completely destroyed.
The tornado then toppled six to eight metal power transmission towers as it moved to the north of the farm. One tower was sheared off from the concrete footings and traveled an estimated 400 yards. Ground scouring was visible along the path of these towers.
The large tornado continued to track east crossing over State Highway 47 where a state radio tower was toppled. The tornado lifted shortly thereafter.  The highest wind speeds were estimated to be from 166 to 200 mph.

Hail in CAMPBELL, SOUTH DAKOTA
From 22-MAY-10 17:35:00 to 22-MAY-10 17:35:00 (CST-6)
Location: HERREID MUNI ARPT
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in EDMUNDS, SOUTH DAKOTA
From 22-MAY-10 18:15:00 to 22-MAY-10 18:15:00 (CST-6)
Location: HOSMER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tornado in BROWN, SOUTH DAKOTA
From 22-MAY-10 19:34:00 to 22-MAY-10 19:40:00 (CST-6)
Location: BARNARD
Tornado F-scale: EF0
Reported by: NWS Storm Survey

A tornado entered into western Brown county from southeast Mcpherson county. The tornado was an EF2 before entering Brown county. The tornado slowly dissipated shortly after entering the county with some tree damage observed.

Hail in EDMUNDS, SOUTH DAKOTA
From 22-MAY-10 19:00:00 to 22-MAY-10 19:00:00 (CST-6)
Location: IPSWICH
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in EDMUNDS, SOUTH DAKOTA
From 22-MAY-10 19:21:00 to 22-MAY-10 19:21:00 (CST-6)
Location: IPSWICH
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Tornado in MCPHERSON, SOUTH DAKOTA
From 22-MAY-10 19:12:00 to 22-MAY-10 19:34:00 (CST-6)
Location: LONG LAKE COLONY
Tornado F-scale: EF2
Reported by: NWS Storm Survey

A tornado entered southeast Mcpherson county from northeast Edmunds county.  The tornado struck a farm along State Highway 45 where a calving shed was completely destroyed with large sections of the roof blown over 100 yards. The tornado then caused moderate damage to a barn with one collapsed wall. Multiple softwood and hardwood trees were uprooted and many power poles were completely snapped near the base. The tornado tore the roof off a turkey barn at the Long Lake Colony. Several Wetonka homes also sustained minor roof damage. The wind speeds were estimated between 111 and 120 mph. The tornado then moved into western Brown county and dissipated.

Tornado in BROWN, SOUTH DAKOTA
From 22-MAY-10 20:10:00 to 22-MAY-10 20:13:00 (CST-6)
Location: HOUGHTON
Tornado F-scale: EF2
Reported by: Trained Spotter

An eighth tornado touched down west of Hecla producing damage to one farm including tearing the roof off of an outbuilding and throwing several grain bins 100 yards or more. Widespread tree damage was also noted. The tornado continued northeast damaging another outbuilding and destroying an empty grain bin before lifting. Wind speeds were estimated between 112 and 120 mph.

Tornado in HYDE, SOUTH DAKOTA
From 22-MAY-10 19:26:00 to 22-MAY-10 19:29:00 (CST-6)
Location: HIGHMORE ARPT
Tornado F-scale: EF1
Reported by: Newspaper

A tornado touched down for a short time in far northeast Hyde county hitting a farm. The tornado damaged or destroyed several large barns, eighteen grain bins, along with the garage on the home. A grain cart was also tipped over by the tornado along with twelve cattle being killed.

Hail in EDMUNDS, SOUTH DAKOTA
From 22-MAY-10 19:25:00 to 22-MAY-10 19:25:00 (CST-6)
Location: IPSWICH
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in HYDE, SOUTH DAKOTA
From 22-MAY-10 20:35:00 to 22-MAY-10 20:35:00 (CST-6)
Location: STEPHAN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BROWN, SOUTH DAKOTA
From 22-MAY-10 20:45:00 to 22-MAY-10 20:45:00 (CST-6)
Location: WARNER
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in SPINK, SOUTH DAKOTA
From 22-MAY-10 21:27:00 to 22-MAY-10 21:27:00 (CST-6)
Location: REDFIELD
Magnitude: 1.75 
Reported by: Storm Chaser

Hail in BROWN, SOUTH DAKOTA
From 22-MAY-10 21:03:00 to 22-MAY-10 21:03:00 (CST-6)
Location: BATH
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in ROBERTS, SOUTH DAKOTA
From 22-MAY-10 22:50:00 to 22-MAY-10 22:50:00 (CST-6)
Location: DAHLBERG
Magnitude: 1.50 
Reported by: Law Enforcement

Thunderstorm Wind in BROWN, SOUTH DAKOTA
From 22-MAY-10 19:48:00 to 22-MAY-10 19:48:00 (CST-6)
Location: BARNARD
Magnitude: 70.00 EG
Reported by: Law Enforcement

Damaging winds downed two very large trees which had fallen across a road. A farmer had the doors ripped off his barn with a horse trailer being moved 150 feet. Another farmer had major damage to several outbuildings.

Thunderstorm Wind in DAY, SOUTH DAKOTA
From 22-MAY-10 22:43:00 to 22-MAY-10 22:43:00 (CST-6)
Location: ROSLYN
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Sixty mph winds were estimated in Roslyn.

Tornado in WALWORTH, SOUTH DAKOTA
From 22-MAY-10 16:31:00 to 22-MAY-10 16:35:00 (CST-6)
Location: AKASKA
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

The first confirmed tornado touchdown was three miles south of Akaska. This was a brief touchdown with no damage reported.

Thunderstorm Wind in SPINK, SOUTH DAKOTA
From 22-MAY-10 03:45:00 to 22-MAY-10 03:45:00 (CST-6)
Location: TULARE
Magnitude: 61.00 EG
Reported by: Broadcast Media

A trailer was flipped over at Cottonwood Lake by seventy mph winds.

Flash Flood in MCPHERSON, SOUTH DAKOTA
From 22-MAY-10 20:10:00 to 22-MAY-10 22:40:00 (CST-6)
Location: LEOLA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy rain of over two inches fell in Leola within one hour causing street flooding throughout town.

Thunderstorm Wind in CLARK, SOUTH DAKOTA
From 22-MAY-10 22:40:00 to 22-MAY-10 22:40:00 (CST-6)
Location: RAYMOND
Magnitude: 61.00 EG
Reported by: Emergency Manager

A pole barn was completely destroyed by seventy mph winds. Two barns had their doors torn off with one sustaining roof damage. An apple tree was also broke off half way up.

Tornado in WALWORTH, SOUTH DAKOTA
From 22-MAY-10 17:16:00 to 22-MAY-10 17:18:00 (CST-6)
Location: JAVA
Tornado F-scale: EF1
Reported by: Trained Spotter

The second tornado touched down eight miles west of Bowdle or two miles south of Highway 12 near State Highway 47.  The tornado knocked down six wooden power poles before it lifted. This is consistent with an EF1 rating with winds from 86 to 110 mph.

Tornado in EDMUNDS, SOUTH DAKOTA
From 22-MAY-10 18:10:00 to 22-MAY-10 18:12:00 (CST-6)
Location: GRETNA
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A fourth tornado touchdown occurred northwest of Roscoe or one-half mile north of the intersection of Highway 12 and State Highway 253. There was no damage reported with this brief touchdown.

Tornado in EDMUNDS, SOUTH DAKOTA
From 22-MAY-10 18:48:00 to 22-MAY-10 18:50:00 (CST-6)
Location: BEEBE
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A fifth tornado touchdown occurred seven miles northwest of Ipswich. The tornado lifted quickly with no damage reported.

Funnel Cloud in FAULK, SOUTH DAKOTA
From 22-MAY-10 19:34:00 to 22-MAY-10 19:34:00 (CST-6)
Location: FAULKTON MUNI ARPT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Funnel Cloud in FAULK, SOUTH DAKOTA
From 22-MAY-10 19:38:00 to 22-MAY-10 19:38:00 (CST-6)
Location: CRESBARD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in WALWORTH, SOUTH DAKOTA
From 22-MAY-10 16:45:00 to 22-MAY-10 16:45:00 (CST-6)
Location: LOWRY
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in WALWORTH, SOUTH DAKOTA
From 22-MAY-10 16:50:00 to 22-MAY-10 16:50:00 (CST-6)
Location: LOWRY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in WALWORTH, SOUTH DAKOTA
From 22-MAY-10 17:13:00 to 22-MAY-10 17:13:00 (CST-6)
Location: JAVA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tornado in WALWORTH, SOUTH DAKOTA
From 22-MAY-10 17:21:00 to 22-MAY-10 17:29:00 (CST-6)
Location: JAVA
Tornado F-scale: EF2
Reported by: NWS Storm Survey

The third tornado formed about four miles west of Bowdle on Highway 12. The tornado came down on a farm or formed immediately to the south of the farm. Several outbuildings were severely damaged with the residence sustaining siding and roof damage. A stock trailer was thrown about 75 yards from its initial point. Tree damage was sustained on the west side of the property with fallen trees leaning west. On the east side of the property, debris was scattered to the northeast. The damage on the farm was consistent with an EF2 rating with wind speeds ranging from 111 to 135 mph. The tornado continued moving northeast crossing into western Edmunds county where it intensified to an EF4.

Tornado in EDMUNDS, SOUTH DAKOTA
From 22-MAY-10 18:48:00 to 22-MAY-10 18:50:00 (CST-6)
Location: BEEBE
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A sixth satellite tornado was observed in conjunction with the main tornado. The tornado was brief and caused no damage.

Tornado in EDMUNDS, SOUTH DAKOTA
From 22-MAY-10 19:01:00 to 22-MAY-10 19:12:00 (CST-6)
Location: IPSWICH TAYLOR ARPT
Tornado F-scale: EF2
Reported by: NWS Storm Survey

The seventh tornado formed in northeast Edmunds county and tracked northeast. The tornado took off sections from the roof of a barn. The tornado then tracked through primarily crop and pasture land to near Deerfield Colony and into southeast Mcpherson county. Sporadic tree damage was observed along the tornado path with many wooden power poles completely sheared off. Wind speeds with this tornado were estimated between 111 and 120 mph.

Hail in WALWORTH, SOUTH DAKOTA
From 22-MAY-10 17:05:00 to 22-MAY-10 17:05:00 (CST-6)
Location: JAVA JCT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in BROWN, SOUTH DAKOTA
From 22-MAY-10 20:53:00 to 22-MAY-10 20:53:00 (CST-6)
Location: ABERDEEN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Funnel Cloud in BROWN, SOUTH DAKOTA
From 22-MAY-10 19:45:00 to 22-MAY-10 19:45:00 (CST-6)
Location: BARNARD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser