A shortwave, negatively tilted trough moved across Eastern Wyoming and over the Central High Plains.  Strong difluence aloft and large scale lift aided in the development of thunderstorms across the Billings Forecast Area. A moist upslope flow combined with 30-40kt wind shear supported severe thunderstorms that produced large hail and damaging winds.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 15-JUN-11 18:37:00 to 15-JUN-11 18:37:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 15-JUN-11 18:40:00 to 15-JUN-11 18:40:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 52.00 EG
Crop damage: 0.00K
Reported by: Law Enforcement

There were numerous reports of large trees and branches down across Billings causing power outages. Downed trees and branches fell on several vehicles. One downed tree branch caused a downed power line that sparked a house fire.

Funnel Cloud in YELLOWSTONE, MONTANA
From 15-JUN-11 18:54:00 to 15-JUN-11 18:54:00 (MST-7)
Location: ACTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in YELLOWSTONE, MONTANA
From 15-JUN-11 19:08:00 to 15-JUN-11 19:08:00 (MST-7)
Location: WORDEN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in BIG HORN, MONTANA
From 15-JUN-11 19:30:00 to 15-JUN-11 19:30:00 (MST-7)
Location: HARDIN
Magnitude: 78.00 EG
Reported by: NWS Storm Survey

Tops of trees and 8 inch limbs were broken.

Thunderstorm Wind in ROSEBUD, MONTANA
From 15-JUN-11 20:30:00 to 15-JUN-11 20:30:00 (MST-7)
Location: COLSTRIP
Magnitude: 70.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

An estimated wind gust of 80 mph was reported from the Town Pump gas station.

Thunderstorm Wind in ROSEBUD, MONTANA
From 15-JUN-11 20:35:00 to 15-JUN-11 20:35:00 (MST-7)
Location: LAME DEER
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

Thunderstorm Wind in ROSEBUD, MONTANA
From 15-JUN-11 20:47:00 to 15-JUN-11 20:47:00 (MST-7)
Location: THURLOW
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Thunderstorm Wind in ROSEBUD, MONTANA
From 15-JUN-11 20:53:00 to 15-JUN-11 20:53:00 (MST-7)
Location: BRANDENBERG
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A wind gust estimated at 70 mph was reported 11 miles north of Brandenberg.

Thunderstorm Wind in CUSTER, MONTANA
From 15-JUN-11 21:05:00 to 15-JUN-11 21:05:00 (MST-7)
Location: GARLAND
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

Thunderstorm Wind in CUSTER, MONTANA
From 15-JUN-11 21:09:00 to 15-JUN-11 21:09:00 (MST-7)
Location: (MLS)WILEY FLD MILES
Magnitude: 55.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Thunderstorm Wind in BIG HORN, MONTANA
From 15-JUN-11 19:30:00 to 15-JUN-11 19:30:00 (MST-7)
Location: HARDIN
Magnitude: 78.00 EG
Reported by: NWS Storm Survey

Severe thunderstorms developed over Billings, MT at approximately 730pm on Wednesday, June 15th. These thunderstorms progressed east across South Central Montana, basically tracking just north of Interstate 90 from Billings to Hardin. The southern flank of the storm produced persistent winds in excess of 60 mph.
At 830 pm, the severe winds enhanced over Hardin, MT. National Weather Service officials conducted a survey of the damage and determined that the damage was the result of microburst winds that surged well south of the associated thunderstorm. Local wind speeds were estimated to have reached speeds of 90 mph. The hardest hit area was the southwest side of Hardin. Several businesses experienced at least partial roof damage. This same area saw numerous trees either snapped off or uprooted and homes with shingles blown off them.

Thunderstorm Wind in YELLOWSTONE, MONTANA
From 15-JUN-11 18:36:00 to 15-JUN-11 18:36:00 (MST-7)
Location: (BIL)LOGAN ARPT BILL
Magnitude: 52.00 EG
Property damage: 0.00K
Reported by: Public

A 30 to 40 foot live Cottonwood tree was snapped off at Pioneer Park.

Thunderstorm Wind in BIG HORN, MONTANA
From 15-JUN-11 19:35:00 to 15-JUN-11 19:35:00 (MST-7)
Location: BIG HORN WYE
Magnitude: 78.00 EG
Reported by: NWS Storm Survey

Microburst winds estimated at 90 mph resulted in several billboards being blown down along Interstate 90.