On July 18, an intensely strong shortwave trough moved to the northeast across Western Montana during the late afternoon and evening hours. The breaking of a strong mid level cap released copious amount of low level instability which aided in the rapid development of severe thunderstorm super cells.

Tornado in FLATHEAD, MONTANA
From 18-JUL-07 19:40:00 to 18-JUL-07 20:30:00 (MST-7)
Location: BIGFORK
Tornado F-scale: EF0
Property damage: 8.00K
Reported by: Public

The public reported a waterspout on Flathead lake along the Flathead/Lake County line. A sailboat at this location was spun around at least once in a counterclockwise direction and then sank.

Thunderstorm Wind in LAKE, MONTANA
From 18-JUL-07 18:55:00 to 18-JUL-07 19:25:00 (MST-7)
Location: PABLO
Magnitude: 78.00 EG
Property damage: 30.00K
Reported by: NWS Storm Survey

National Weather Service storm survey crew saw numerous trees and several power poles down along the storm's track. Two structures received roof damage. The damage observed was indicative of straight line winds. A flag pole was bent in half southwest of Polson. Based upon the damage observed, winds were estimated to be between 80 to 100 mph.

Tornado in LAKE, MONTANA
From 18-JUL-07 18:50:00 to 18-JUL-07 19:40:00 (MST-7)
Location: PABLO
Tornado F-scale: EF0
Property damage: 8.00K
Reported by: Public

The public reported a tornado 10 miles west northwest of Pablo and also a waterspout over Flathead Lake north of Polson. In addition, a sail boat (located on the Flathead County/Lake County line) was spun around at least once in a counterclockwise direction and then sank.

Thunderstorm Wind in FLATHEAD, MONTANA
From 18-JUL-07 19:25:00 to 18-JUL-07 19:55:00 (MST-7)
Location: LAKESIDE
Magnitude: 78.00 EG
Property damage: 300.00K
Reported by: NWS Storm Survey

Numerous trees and power poles were blown down along the northern shores of Flathead lake. The roof to Carpenter's Arena near Kalispell was blown off. Damage to two other roofs was observed. One small grain silo was blown over near Somers. The damage observed from the NWS storm survey crew was indicative of straight line wind damage. Based upon the damage observed, winds were estimated to be between 80 and 100 mph.

Thunderstorm Wind in LINCOLN, MONTANA
From 18-JUL-07 19:20:00 to 18-JUL-07 19:35:00 (MST-7)
Location: LIBBY
Magnitude: 61.00 EG
Property damage: 35.00K
Reported by: Trained Spotter

Estimated thunderstorm wind gusts to 70 mph produced substantial structural damage to the drive-in theater and the town ball park. Numerous large trees were also blown down.

Thunderstorm Wind in SANDERS, MONTANA
From 18-JUL-07 20:50:00 to 18-JUL-07 20:58:00 (MST-7)
Location: LONE PINE
Magnitude: 61.00 EG
Reported by: Public

Several large trees blown down. Windows blown out on mobile homes from straight line winds.

Hail in FLATHEAD, MONTANA
From 18-JUL-07 20:35:00 to 18-JUL-07 20:35:00 (MST-7)
Location: KALISPELL
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Nickel size hail was reported covering the ground in Kalispell. Power was also reported out to most of the county.

Hail in SANDERS, MONTANA
From 18-JUL-07 18:30:00 to 18-JUL-07 18:30:00 (MST-7)
Location: PERMA
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency Management reported nickel size hail in Perma.

Hail in MINERAL, MONTANA
From 18-JUL-07 17:44:00 to 18-JUL-07 17:44:00 (MST-7)
Location: TARKIO
Magnitude: 1.75 
Reported by: Broadcast Media

Golf ball size hail was reported to KECI TV Meteorologist from a weather spotter in Tarkio.