A very strong and unseasonably cold upper level low pressure system that was tracking across the northern plains brought a strong low level jet to the region during the early morning hours of June 11th.  The warm and unstable air that worked north into the region helped spawn early morning severe thunderstorms across eastern Nebraska and southwest Iowa.  Later that day as the upper level system worked into the central Dakotas, a cold front pushed across the region.  This helped set off another round of thunderstorms that developed over east central Nebraska by late afternoon.
Isolated small supercell thunderstorms initially developed ahead of the cold front over eastern Nebraska, but they were quickly overtaken by a broken line of larger supercell thunderstorms, some of the heavy precipitation type, that developed along the cold front.  Cell mergers and training were observed well into the evening hours as the activity quickly spread across southwest Iowa.  The storms produced a total of 8 confirmed tornadoes in the Omaha/Valley warning area which covers eastern Nebraska and southwest Iowa.

Tornado in MONONA, IOWA
From 11-JUN-08 17:36:00 to 11-JUN-08 17:45:00 (CST-6)
Location: BLENCOE
Tornado F-scale: EF3
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado tragically hit a boyscout camp north of Little Sioux Iowa killing 4 young scouts.  The tornado initially touched down in Burt county Nebraska, crossed into Harrison county Iowa near mile marker 97 on Interstate 29, and then finally crossed into Monona county Iowa about 4 miles north of Little Sioux.  In Monona county the tornado entered the Little Sioux Scout Ranch, destroying the rangers home near the entrance of the park giving it a rating of EF3.  The storm then blew down trees and destroyed bunk houses at the camp. Four scouts were killed in one bunk house when a brick chimney collapsed on them.  In total 48 people were injured at the camp.  The tornado continued to topple trees as it tracked into Preparation Canyon State Park.  Just before it entered the park a farmstead sustained damage.  The tornado hit another farmstead about 2.5 miles southwest of Moorhead where trees were blown down and sheds damaged.  The tornado then began to weaken and finally lifted about 2 miles southwest of Moorhead.  The total path length was around 14 miles.

Flood in POTTAWATTAMIE, IOWA
From 11-JUN-08 23:15:00 to 12-JUN-08 18:30:00 (CST-6)
Location: HANCOCK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

A week of heavy rain producing thunderstorms through June 11th fell across the Nishnabotna River basin in southwest Iowa.  The heavy rain caused flooding along the West Nishnabotna from around Hancock, in Pottawattamie county, through Randolph in Fremont county to its merger with the East Nishnabotna River near Hamburg.  The river at Hancock in Pottawattamie county reached an 18.5 foot crest around 1215pm CDT on June 12th, flood stage is 14 feet.  The river at Hancock fell below flood stage during the evening hours of June 12th.  The flooding closed several county roads and also flooded agricultural lowlands in the area.

Tornado in SHELBY, IOWA
From 11-JUN-08 19:05:00 to 11-JUN-08 19:07:00 (CST-6)
Location: DEFIANCE
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

An apparent tornado downed 30 to 40 trees and damaged a farm outbuilding 4 miles south of Defiance.

Thunderstorm Wind in HARRISON, IOWA
From 11-JUN-08 17:30:00 to 11-JUN-08 17:30:00 (CST-6)
Location: RIVER SIOUX
Magnitude: 55.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Thunderstorm wind gusts estimated at over 60 mph knocked down large tree limbs and toppled a dead tree knocking power out to the area.

Tornado in MONONA, IOWA
From 11-JUN-08 18:20:00 to 11-JUN-08 18:22:00 (CST-6)
Location: MAPLETON
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

A brief tornado touched down 6 miles northeast of Castana causing mainly just tree damage.

Tornado in SHELBY, IOWA
From 11-JUN-08 18:59:00 to 11-JUN-08 19:02:00 (CST-6)
Location: DEFIANCE
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A tornado touched down briefly northwest of Defiance.  The tornado caused mainly just tree damage.

Hail in SHELBY, IOWA
From 11-JUN-08 19:15:00 to 11-JUN-08 19:15:00 (CST-6)
Location: IRWIN
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Thunderstorm Wind in HARRISON, IOWA
From 11-JUN-08 19:00:00 to 11-JUN-08 19:00:00 (CST-6)
Location: HARD SCRATCH
Magnitude: 55.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm wind gusts estimated at over 60 mph blew 2 windows out of a house and knocked down a few branches.

Flash Flood in POTTAWATTAMIE, IOWA
From 11-JUN-08 21:52:00 to 11-JUN-08 23:52:00 (CST-6)
Location: LAKE MANAWA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Local law enforcement reported that flash flooding occurred over a few roads in south Council Bluffs.

Flood in PAGE, IOWA
From 12-JUN-08 02:30:00 to 13-JUN-08 03:45:00 (CST-6)
Location: HEPBURN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

A week of heavy rain producing thunderstorms through June 11th fell across the Nodaway River basin in southwest Iowa.  The heavy rain caused flooding along the Nodaway River from around Villisca downstream through Clarinda to around Braddyville.  The river at Clarinda reached a 22.7 foot crest at 430pm CDT on June 12, flood stage is 19 feet.  The river fell below flood stage at Clarinda during the early morning hours of June 13th.  The flooding closed several county roads and also flooded farm fields in eastern Page county.

Tornado in POTTAWATTAMIE, IOWA
From 11-JUN-08 18:23:00 to 11-JUN-08 18:24:00 (CST-6)
Location: LOVELAND
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

This was the second tornado that was observed by researchers tracking this storm.  The tornado touched down briefly just northeast of exit 72 on Interstate 29 and lifted a little to the northeast, doing no apparent damage.  The researchers were using DOW, a mobile radar system, and besides being visually seen by the researches, it also produced a tornadic signature on the DOW system.

Flood in FREMONT, IOWA
From 11-JUN-08 22:30:00 to 13-JUN-08 13:30:00 (CST-6)
Location: RIVERTON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

A week of heavy rain producing thunderstorms through June 11th fell across the Nishnabotna River basin in southwest Iowa.  The heavy rain caused flooding along the East Nishnabotna from around Elliott downstream through the Red Oak area and then into Fremont county where it merges with the West Nishnabotna River near Hamburg.  The river at Red Oak reached a 24 foot crest around 415am CDT on June 13th, flood stage is 18 feet.  The river at Red Oak fell below flood stage in the mid afternoon hours of June 13th.  The flooding closed a four-mile stretch of Highway 275 near Hamburg from the Missouri state line north, and also closed several county roads, especially around Riverton.  Agricultural lowlands in the area were also flooded.

Flood in MONTGOMERY, IOWA
From 11-JUN-08 22:30:00 to 13-JUN-08 13:30:00 (CST-6)
Location: ELLIOTT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

A week of heavy rain producing thunderstorms through June 11th fell across the Nishnabotna, Tarkio and Nodaway River basins in southwest Iowa causing some flooding along each.  Flooding along the East Nishnabotna River was noted from around Elliott downstream through the Red Oak area and then into Fremont county where it merges with the West Nishnabotna River near Hamburg.  The river at Red Oak reached a 24 foot crest around 415am CDT on June 13th, flood stage is 18 feet.  The river at Red Oak fell below flood stage in the mid afternoon hours of June 13th.  The flooding closed several county roads and also flooded agricultural lowlands in the area.  Flooding was also observed along the Tarkio River near Stanton which submerged boat docks and caused the closure of 6 campsites at a local State Park. Flooding along the East Nodaway River near Villisca prompted the closing of a county road in the area.

Flood in FREMONT, IOWA
From 11-JUN-08 22:30:00 to 13-JUN-08 14:30:00 (CST-6)
Location: RANDOLPH
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

A week of heavy rain producing thunderstorms through June 11th fell across the Nishnabotna River basin in southwest Iowa.  The heavy rain caused flooding along the West Nishnabotna from around Hancock, in Pottawattamie county, through Randolph in Fremont county to its merger with the East Nishnabotna River near Hamburg.  The river at Randolph reached a 23.8 foot crest around 815pm CDT on June 12th, flood stage is 19 feet.  The river at Randolph fell below flood stage during the evening hours of June 13th.  The flooding closed several county roads and also flooded agricultural lowlands in the area.

Flood in POTTAWATTAMIE, IOWA
From 11-JUN-08 00:30:00 to 12-JUN-08 05:00:00 (CST-6)
Location: LOVELAND
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Thunderstorms dropped heavy rain on the Boyer River basin on June 11th.  The heavy rain caused flooding along the Boyer River from around Woodbine to Missouri Valley.  The river at Logan crested at 19.7 feet at 215am CDT on June 12th. Flood stage at Logan is 19 feet.  The flooding affected mainly agricultural lowlands in the area.

Tornado in HARRISON, IOWA
From 11-JUN-08 17:27:00 to 11-JUN-08 17:36:00 (CST-6)
Location: RIVER SIOUX
Tornado F-scale: EF2
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This is a continuation of the tornado that initially touched down in Burt county Nebraska, about 4.5 miles west of Little Sioux Iowa.  The tornado eventually reached EF3 strength in Monona county when it hit a boyscout camp where 4 fatalities and 48 injuries occurred.  The tornado crossed into Harrison county near mile marker 97 on Interstate 29 where a semi-truck was flipped.  The tornado snapped power poles northeast of there with an estimated strength of EF2 in Harrison county.  The tornado then crossed into Monona county Iowa about 4 miles north of Little Sioux.

Flash Flood in POTTAWATTAMIE, IOWA
From 12-JUN-08 00:30:00 to 12-JUN-08 02:30:00 (CST-6)
Location: OAKLAND
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Flash flooding was reported across a road a mile west of Oakland.

Tornado in POTTAWATTAMIE, IOWA
From 11-JUN-08 18:20:00 to 11-JUN-08 18:22:00 (CST-6)
Location: LOVELAND
Tornado F-scale: EF1
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

According to researchers tracking this storm, who were using DOW - a mobile radar system, this brief tornado touched down around 2 miles west southwest of exit 72 on Interstate 29 and lifted about 1/2 mile east of the exit.  The tornado downed 1 tree but did little other damage.  Besides being visually seen by the researchers, it also produced a tornadic signature on the DOW system.