A mid-level southwest 50 knot jet maximum combined with high moisture and very warm temperatures provided the prime environment for strong supercells. These cells brought both severe wind and hail.

Thunderstorm Wind in DEER LODGE, MONTANA
From 17-JUL-13 16:20:00 to 17-JUL-13 16:20:00 (MST-7)
Location: WEST VLY
Magnitude: 61.00 EG
Property damage: 18.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

On July 17, 2013, a multicellular thunderstorm developed a gustnado causing a roof to be torn off of a closed garage and thrown into a power pole. The power pole broke off leaving live wires on the ground. Another shed immediately downstream was torn apart and thrown across the yard. The path of the damage was about 200 yards long and 50 to 100 feet wide. A neighbor watching the event occur from a few feet away, reported swirling debris for at least 10 to 15 seconds.

Hail in FLATHEAD, MONTANA
From 17-JUL-13 14:30:00 to 17-JUL-13 14:30:00 (MST-7)
Location: KALISPELL
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A right-moving supercell that tracked from just southwest of Marion moved over Kila and Kalispell. A person from the public in Kalispell measured 1 inch hail.

Hail in MISSOULA, MONTANA
From 17-JUL-13 14:30:00 to 17-JUL-13 14:30:00 (MST-7)
Location: MISSOULA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

A right-moving supercell moved across the Missoula International airport and brought penny sized hail.

Hail in LAKE, MONTANA
From 17-JUL-13 14:29:00 to 17-JUL-13 14:29:00 (MST-7)
Location: ROLLINS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter on the east side of Flathead Lake reported an estimated 1 hail with no damage to cherry trees.

Thunderstorm Wind in POWELL, MONTANA
From 17-JUL-13 15:10:00 to 17-JUL-13 15:10:00 (MST-7)
Location: AVON
Magnitude: 52.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Public

A very large right-moving supercell tracked east-northeast from Goldcreek to north of Avon bringing with it large hail, severe winds and heavy rain. A rancher 5 miles north of Avon reported a totaled barn, several trees that were either uprooted or broken in half. One of those trees uprooted was a 24 cottonwood.

Hail in POWELL, MONTANA
From 17-JUL-13 15:10:00 to 17-JUL-13 15:10:00 (MST-7)
Location: AVON
Magnitude: 1.25 
Property damage: 3.00K
Crop damage: 50.00K
Reported by: Public

A very large right-moving supercell brought hail and wind damage to ranchers north of Avon. A rancher reported up to half dollar sized hail that brought considerable damage to their hay crop, and windows.

Thunderstorm Wind in POWELL, MONTANA
From 17-JUL-13 15:12:00 to 17-JUL-13 15:12:00 (MST-7)
Location: AVON
Magnitude: 52.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Public

A very large supercell brought estimated 60 mph wind gusts that caused several trees to either uproot or break in half. Most of the trees fell in an easterly direction.

Thunderstorm Wind in LINCOLN, MONTANA
From 17-JUL-13 14:10:00 to 17-JUL-13 14:22:00 (MST-7)
Location: ROOSVILLE
Magnitude: 75.00 MG
Property damage: 10.50K
Crop damage: 0.00K
Reported by: AWOS

As a right-moving supercell approached the Eureka airport, it unleashed severe downdraft winds as reported by the AWOS sensor from the southwest direction for at least 12 minutes. The observer at the airport reported that one airplane flipped over, steel siding was torn off from a hanger, a telephone booth blew over, and an awning structure blew off.

Hail in LINCOLN, MONTANA
From 17-JUL-13 14:10:00 to 17-JUL-13 14:20:00 (MST-7)
Location: ROOSVILLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Local businesses north of Eureka reported damage to outside equipment due to the wind and hail estimated at one inch.

Thunderstorm Wind in LINCOLN, MONTANA
From 17-JUL-13 14:10:00 to 17-JUL-13 14:22:00 (MST-7)
Location: ROOSVILLE
Magnitude: 70.00 EG
Property damage: 4.70K
Crop damage: 0.00K
Reported by: Public

On the afternoon of Wednesday July 17th 2013, a right-moving supercell thunderstorm produced up to one inch hail with estimated winds near 80 mph just north of the Eureka airport in Montana. According to homeowners in the area, the mostly marble-sized hail flew sideways due to the hurricane force wind damaging roof shingles, siding, windows, paint and vehicles, and shredding vegetation. Trees toppled over in a northeast direction implying that winds could have been from the southwest.

Hail in LINCOLN, MONTANA
From 17-JUL-13 14:10:00 to 17-JUL-13 14:22:00 (MST-7)
Location: ROOSVILLE
Magnitude: 1.00 
Property damage: 6.00K
Crop damage: 0.50K
Reported by: Public

On the afternoon of Wednesday July 17th 2013, a right-moving supercell thunderstorm produced up to one inch hail with estimated winds near 80 mph just north of the Eureka airport in Montana. According to homeowners in the area, the mostly marble-sized hail flew sideways due to the hurricane force wind damaging roof shingles, siding, windows, paint and vehicles, and shredding vegetation. Trees toppled over in a northeast direction implying that winds could have been from the southwest.

Thunderstorm Wind in LINCOLN, MONTANA
From 17-JUL-13 14:10:00 to 17-JUL-13 14:20:00 (MST-7)
Location: ROOSVILLE
Magnitude: 70.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Public

Local businesses located north of Eureka reported damage to outside equipment due to the wind and hail. Several 4 inch trees broke in half laying down pointing east-northeast. Two fir trees with a base diameter of 16 inches were lost: one fell over while the other broke in half. The wind ripped tin siding off of the buildings.

Thunderstorm Wind in LINCOLN, MONTANA
From 17-JUL-13 14:05:00 to 17-JUL-13 14:15:00 (MST-7)
Location: EUREKA ARPT
Magnitude: 70.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Public

On the afternoon of Wednesday July 17th 2013, a right-moving supercell thunderstorm moved across the region causing severe wind and hail. A local business northwest of Eureka reported at least 30 trees toppled due to the strong wind. Also the combination of wind and hail damaged the greens at a nearby golf course.

Hail in LINCOLN, MONTANA
From 17-JUL-13 14:00:00 to 17-JUL-13 14:10:00 (MST-7)
Location: REXFORD
Magnitude: 1.25 
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Public

On the afternoon of Wednesday July 17th 2013, a right-moving supercell thunderstorm developed near Troy and tracked north and east across Rexford. A local business in Rexford reported structure and vehicle damage due to the estimated half-dollar hail. Several teenagers received bruises from the hail when they were on the shore of Lake Kookanusa. They estimated the thunderstorm wind gusts to 50 mph.

Hail in FLATHEAD, MONTANA
From 17-JUL-13 14:38:00 to 17-JUL-13 14:38:00 (MST-7)
Location: JESSUP
Magnitude: 1.00 
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Public

A right-moving supercell developed just southeast of Kila and tracked north and east across the Creston area. A local business sustained considerable damage due to the estimated quarter size hail.

Hail in FLATHEAD, MONTANA
From 17-JUL-13 14:40:00 to 17-JUL-13 14:40:00 (MST-7)
Location: CRESTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A right-moving supercell developed just southeast of Kila and tracked north and east across the Creston area.  A local resident measured up to one inch hail in diameter that covered the ground to three inches deep.

Hail in FLATHEAD, MONTANA
From 17-JUL-13 14:38:00 to 17-JUL-13 14:38:00 (MST-7)
Location: CRESTON
Magnitude: 0.50 
Property damage: 0.50K
Crop damage: 5.00K
Reported by: Public

A right-moving supercell developed just southeast of Kila and tracked north and east across the Creston area.  A farmer reported hail accumulation between 6 and 8 inches that dented vehicle hoods and damaged barley, spring wheat and canola crops. The half inch hail was estimated.

Hail in FLATHEAD, MONTANA
From 17-JUL-13 14:40:00 to 17-JUL-13 14:40:00 (MST-7)
Location: CRESTON
Magnitude: 1.75 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

A right-moving supercell developed just southeast of Kila and tracked north and east across the Creston area. At least two different people from the Many Lakes residential area reported jagged edged-hail to the estimated size of golf balls. One person said the hail looked like it had marble sized pieces frozen together. Multiple homeowners reported hail damage to their vehicles.

Hail in FLATHEAD, MONTANA
From 17-JUL-13 14:15:00 to 17-JUL-13 14:15:00 (MST-7)
Location: KILA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A right-moving supercell formed 30 miles southwest of Marion and tracked northeast around 40 mph to just north of Kila.  A trained spotter located 2 miles north of Kila measured penny sized hail.

Hail in MISSOULA, MONTANA
From 17-JUL-13 15:00:00 to 17-JUL-13 15:00:00 (MST-7)
Location: CLEARWATER
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A long-lasting right-moving supercell that tracked over the Missoula International airport continued east-northeast between Seeley Lake and Woodworth. A person from the public estimated penny sized hail just northwest of Woodworth that lasted for 5 minutes. The Missoula Doppler radar observed a three body scatter spike between 12 and 18 thousand feet MSL with this storm which is indicative of large hail.

Hail in POWELL, MONTANA
From 17-JUL-13 15:16:00 to 17-JUL-13 15:16:00 (MST-7)
Location: AVON
Magnitude: 1.50 
Property damage: 13.00K
Crop damage: 50.00K
Reported by: Public

A very large right-moving supercell unleashed up to ping pong sized hail that decimated a four to five foot tall hay crop. The hail covered the ground to a depth of 2 inches in spots. At least 10 windows were broken. Paint was chipped off from homes. Other damage included a greenhouse roof, vehicle windows and vegetation.

Hail in LINCOLN, MONTANA
From 17-JUL-13 14:10:00 to 17-JUL-13 14:20:00 (MST-7)
Location: EUREKA ARPT
Magnitude: 1.00 
Property damage: 0.50K
Crop damage: 1.00K
Reported by: Public

A resident reported damage to window screens and 150 fruit trees by the combination of hail and strong wind. They reported that the estimated one inch hail had a disc-shaped appearance.