Severe thunderstorms produced extensive damage as they moved across the Urban Corridor.  At Denver International Airport alone, large hail up to golfball size, very heavy rain and wind gusts to 59 mph caused substantial damage to 40 planes and stranded approximately 1,500 passengers overnight.  Frontier and United Airlines were hardest hit as dozens of planes were taken out of service for repairs; forcing the cancellation of at least 220 flights over the next several days.  Damage to the aircrafts alone was nearly $5 million.   In addition, 83 cars in airport parking lots were damaged, along with some police cars and maintenance vehicles.  In Watkins, two people suffered minor injuries and 35 to 40 homes were damaged.  As many as 200 residents in a mobile home park were left homeless by the storm, forcing the Red Cross to open a shelter at Bennett High School.  The trailer park contained 52 mobile homes, 14 recreational vehicles, 3 houses and a commercial building.  Hailstones the size of softballs cratered the north sides of the mobile homes.  Some farmers in the area said they lost as much as 85 percent of their total wheat crop.  Power lines were also damaged which affected about 1,200 customers in Watkins.  The strong winds also flipped over a tractor-trailer rig on Interstate 70 near Watkins Road.  Insurance claims for the Watkins, Bennett and Brighton areas was estimated to be $17 million.  The total damage estimate across the entire Urban Corridor, was $164.8 million, and included 17,200 automobile claims and 12,600 homeowner claims.
In addition, thunderstorms producing very heavy rainfall, caused flash flooding in the Four Mile Canyon burn scar west of Boulder.  Three homes reportedly had water up to the windows with water flowing into structures at Fourmile Canyon Road and Gold Run Road.  The heavy rain caused a 4-ft surge along Fourmile Creek through Orodell and into the entry of Boulder Creek.  Several roads were affected which restricted access to the area.  Roads were closed due to water and debris.  Private bridges and drives were washed out and several residents were stranded and later rescued.  Numerous cars were damaged in debris flows and several structures suffered flood damage but were not destroyed.

Hail in LARIMER, COLORADO
From 13-JUL-11 18:39:00 to 13-JUL-11 18:39:00 (MST-7)
Location: HARMONY
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:37:00 to 13-JUL-11 18:37:00 (MST-7)
Location: MASONVILLE
Magnitude: 1.75 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:34:00 to 13-JUL-11 18:34:00 (MST-7)
Location: LOVELAND
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:28:00 to 13-JUL-11 18:28:00 (MST-7)
Location: LOVELAND
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:25:00 to 13-JUL-11 18:25:00 (MST-7)
Location: MASONVILLE
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:45:00 to 13-JUL-11 18:45:00 (MST-7)
Location: DRAKES
Magnitude: 1.75 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:43:00 to 13-JUL-11 18:43:00 (MST-7)
Location: HARMONY
Magnitude: 1.25 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:42:00 to 13-JUL-11 18:42:00 (MST-7)
Location: HARMONY
Magnitude: 1.00 
Reported by: Amateur Radio

Hail in LARIMER, COLORADO
From 13-JUL-11 18:38:00 to 13-JUL-11 18:38:00 (MST-7)
Location: HARMONY
Magnitude: 1.25 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:52:00 to 13-JUL-11 18:52:00 (MST-7)
Location: LOVELAND
Magnitude: 1.75 
Reported by: State Official

Hail in LARIMER, COLORADO
From 13-JUL-11 18:49:00 to 13-JUL-11 18:49:00 (MST-7)
Location: HARMONY
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:45:00 to 13-JUL-11 18:45:00 (MST-7)
Location: HARMONY
Magnitude: 1.75 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:45:00 to 13-JUL-11 18:45:00 (MST-7)
Location: DRAKES
Magnitude: 1.50 
Reported by: Trained Spotter

Hail in JEFFERSON, COLORADO
From 13-JUL-11 18:30:00 to 13-JUL-11 18:30:00 (MST-7)
Location: BUFFALO CREEK
Magnitude: 2.00 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:45:00 to 13-JUL-11 18:45:00 (MST-7)
Location: HARMONY
Magnitude: 1.50 
Reported by: Trained Spotter

Hail in DENVER, COLORADO
From 13-JUL-11 20:31:00 to 13-JUL-11 20:31:00 (MST-7)
Location: LOWRY AFB
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:00:00 to 13-JUL-11 18:00:00 (MST-7)
Location: LOVELAND
Magnitude: 1.00 
Reported by: Trained Spotter

Thunderstorm Wind in DENVER, COLORADO
From 13-JUL-11 20:30:00 to 13-JUL-11 20:30:00 (MST-7)
Location: LOWRY AFB
Magnitude: 51.00 MG
Reported by: ASOS

Hail in ADAMS, COLORADO
From 13-JUL-11 20:40:00 to 13-JUL-11 20:40:00 (MST-7)
Location: WATKINS
Magnitude: 4.50 
Property damage: 164.80M
Reported by: Broadcast Media

Flash Flood in BOULDER, COLORADO
From 13-JUL-11 18:00:00 to 13-JUL-11 20:51:00 (MST-7)
Location: JAMESTOWN
Flood cause: Heavy Rain / Burn Area
Property damage: 300.00K
Crop damage: 20.00K
Reported by: Emergency Manager

Heavy rain produced significant flash flooding in the Fourmile burn scar.

Hail in ELBERT, COLORADO
From 13-JUL-11 13:31:00 to 13-JUL-11 13:31:00 (MST-7)
Location: SIMLA
Magnitude: 1.25 
Reported by: Trained Spotter

Hail in ELBERT, COLORADO
From 13-JUL-11 13:22:00 to 13-JUL-11 13:22:00 (MST-7)
Location: SIMLA
Magnitude: 1.00 
Reported by: Storm Chaser

Hail in ELBERT, COLORADO
From 13-JUL-11 15:20:00 to 13-JUL-11 15:20:00 (MST-7)
Location: ELBERT
Magnitude: 1.00 
Reported by: NWS Employee

Hail in ELBERT, COLORADO
From 13-JUL-11 14:00:00 to 13-JUL-11 14:00:00 (MST-7)
Location: MATHESON
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Hail in JEFFERSON, COLORADO
From 13-JUL-11 17:09:00 to 13-JUL-11 17:09:00 (MST-7)
Location: LAKEWOOD
Magnitude: 1.25 
Reported by: Trained Spotter

Hail in JEFFERSON, COLORADO
From 13-JUL-11 17:04:00 to 13-JUL-11 17:04:00 (MST-7)
Location: LAKEWOOD
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in DENVER, COLORADO
From 13-JUL-11 17:14:00 to 13-JUL-11 17:14:00 (MST-7)
Location: SOUTH DENVER
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in JEFFERSON, COLORADO
From 13-JUL-11 17:08:00 to 13-JUL-11 17:08:00 (MST-7)
Location: LAKEWOOD
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in DENVER, COLORADO
From 13-JUL-11 17:26:00 to 13-JUL-11 17:26:00 (MST-7)
Location: DENVER
Magnitude: 1.50 
Reported by: Storm Chaser

Hail in JEFFERSON, COLORADO
From 13-JUL-11 17:24:00 to 13-JUL-11 17:24:00 (MST-7)
Location: LAKEWOOD
Magnitude: 1.25 
Reported by: Trained Spotter

Hail in DENVER, COLORADO
From 13-JUL-11 17:20:00 to 13-JUL-11 17:20:00 (MST-7)
Location: DENVER
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in DENVER, COLORADO
From 13-JUL-11 17:17:00 to 13-JUL-11 17:17:00 (MST-7)
Location: DENVER
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in ARAPAHOE, COLORADO
From 13-JUL-11 17:34:00 to 13-JUL-11 17:34:00 (MST-7)
Location: SHERIDAN
Magnitude: 1.25 
Reported by: Trained Spotter

Hail in DENVER, COLORADO
From 13-JUL-11 17:40:00 to 13-JUL-11 17:40:00 (MST-7)
Location: SOUTH DENVER
Magnitude: 1.00 
Reported by: NWS Employee

Hail in BOULDER, COLORADO
From 13-JUL-11 18:17:00 to 13-JUL-11 18:17:00 (MST-7)
Location: LYONS
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in LARIMER, COLORADO
From 13-JUL-11 18:11:00 to 13-JUL-11 18:11:00 (MST-7)
Location: DRAKE
Magnitude: 1.00 
Reported by: Trained Spotter