Severe thunderstorms occurred in and around the Denver area.  The storms produced large hail, from quarter to golfball size.  Frontier Airlines canceled 16 flights, when several planes sustained hail damage.  Forty flights at Denver International Airport were either delayed or canceled. Some homes in Green Valley Ranch east of Denver were damaged by hail.  Several vehicles were also damaged.  Five short lived tornadoes touched down but no damage was reported.
The storms also produced heavy rain and strong damaging winds.  The wind downed trees and power lines east of Denver.  The heavy rain and hail, up to 6 inches deep in spots, caused street flooding around the metro area.  The hailstorm at Dick���s Sporting Goods Park knocked out power to the stadium where the 4A and 5A girls soccer championship games were about to be played.  The inclement weather snarled traffic on Interstate 70, Pe��a Boulevard, U.S. 85 and elsewhere due to the flooded roads. In some areas, snow plows were called out to clear the hail.  Parts of Tower Road and Peoria Street, and other roads in Commerce City, were closed through the late evening hours, because of standing water.  Several vehicles stalled in standing water where water pooled in the underpasses.

Hail in ADAMS, COLORADO
From 21-MAY-14 14:50:00 to 21-MAY-14 14:50:00 (MST-7)
Location: BENNETT
Magnitude: 1.50 
Reported by: Trained Spotter

Tornado in ADAMS, COLORADO
From 21-MAY-14 13:45:00 to 21-MAY-14 13:45:00 (MST-7)
Location: WATKINS
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: County Official

A tornado touched down briefly.  No damage was observed.

Tornado in ARAPAHOE, COLORADO
From 21-MAY-14 13:05:00 to 21-MAY-14 13:10:00 (MST-7)
Location: (BKF)BUCKLEY AIR FORCE BASE
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A tornado touched down briefly.  No damage was reported.

Hail in JEFFERSON, COLORADO
From 21-MAY-14 13:03:00 to 21-MAY-14 13:03:00 (MST-7)
Location: LAKEWOOD
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in JEFFERSON, COLORADO
From 21-MAY-14 12:20:00 to 21-MAY-14 12:20:00 (MST-7)
Location: ASPEN PARK
Magnitude: 1.00 
Reported by: CoCoRaHS

Tornado in ADAMS, COLORADO
From 21-MAY-14 16:06:00 to 21-MAY-14 16:06:00 (MST-7)
Location: STRASBURG
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A tornado touched down briefly.  No damage was observed.

Thunderstorm Wind in ARAPAHOE, COLORADO
From 21-MAY-14 15:50:00 to 21-MAY-14 15:50:00 (MST-7)
Location: BYERS
Magnitude: 60.00 EG
Reported by: Trained Spotter

Thunderstorm winds downed trees and power lines.

Hail in ADAMS, COLORADO
From 21-MAY-14 15:39:00 to 21-MAY-14 15:39:00 (MST-7)
Location: BENNETT
Magnitude: 1.75 
Reported by: Trained Spotter

Tornado in ARAPAHOE, COLORADO
From 21-MAY-14 15:20:00 to 21-MAY-14 15:25:00 (MST-7)
Location: BYERS
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A tornado touched down for a few minutes.  No damage was observed.

Hail in ADAMS, COLORADO
From 21-MAY-14 14:39:00 to 21-MAY-14 14:39:00 (MST-7)
Location: BENNETT
Magnitude: 1.75 
Reported by: Trained Spotter

Hail in DENVER, COLORADO
From 21-MAY-14 14:00:00 to 21-MAY-14 14:00:00 (MST-7)
Location: (DEN)DENVER INTL ARP
Magnitude: 1.00 
Reported by: Trained Spotter

Large hail damaged some vehicles and shingles.

Hail in JEFFERSON, COLORADO
From 21-MAY-14 13:46:00 to 21-MAY-14 13:46:00 (MST-7)
Location: COLUMBINE
Magnitude: 1.50 
Reported by: Trained Spotter

Hail in ARAPAHOE, COLORADO
From 21-MAY-14 12:34:00 to 21-MAY-14 12:34:00 (MST-7)
Location: (BKF)BUCKLEY AIR FORCE BASE
Magnitude: 1.00 
Reported by: Trained Spotter

Tornado in ADAMS, COLORADO
From 21-MAY-14 13:30:00 to 21-MAY-14 13:30:00 (MST-7)
Location: AURORA
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A tornado touched down briefly.  No damage was observed.

Hail in ARAPAHOE, COLORADO
From 21-MAY-14 13:25:00 to 21-MAY-14 13:25:00 (MST-7)
Location: (BKF)BUCKLEY AIR FORCE BASE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter