The atmosphere had warmed and dried from the first 90 degree day of the summer on Monday June 28. By Tuesday June 29, very unstable air associated with increasing southwesterly flow and moisture aloft provided the ingredients for a severe weather event.  A strong shortwave associated with an approaching jet stream approached the area. The first severe storm developed Tuesday afternoon over Ovando in Powell County with wind gusts up to 60 mph blowing trees down. By early evening, the transition had already taken place for large hail producers as large hail was noted first near Condon. Two severe storms passed near Missoula and Lolo at 940 PM and again at 11 PM  with large hail and wind. The most significant severe weather occurred between Stevensville and Florence, as a line of storms produced outflow damaging winds estimated at 88 to 100 mph between 1045 PM to 1130 PM.

Hail in POWELL, MONTANA
From 29-JUN-10 14:50:00 to 29-JUN-10 14:58:00 (MST-7)
Location: OVANDO
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

An employee at Trixi's Bar in Ovando estimated nickel size hail and heavy rain.

Hail in MISSOULA, MONTANA
From 29-JUN-10 20:50:00 to 29-JUN-10 21:15:00 (MST-7)
Location: (MSO)MISSOULA INTL A
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

A NWS employee measured one inch size hail at his residence north of Missoula in the Prospect Creek neighborhood.

Thunderstorm Wind in POWELL, MONTANA
From 29-JUN-10 14:50:00 to 29-JUN-10 14:58:00 (MST-7)
Location: OVANDO
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported a cottonwood tree fallen across the road.

Thunderstorm Wind in MISSOULA, MONTANA
From 29-JUN-10 20:40:00 to 29-JUN-10 21:11:00 (MST-7)
Location: CARLTON
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Media shared photos of a backyard trampoline blown up against the side of a home.

Hail in MISSOULA, MONTANA
From 29-JUN-10 17:25:00 to 29-JUN-10 17:42:00 (MST-7)
Location: CONDON USFS ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

The Swan River Lodge reported periods of one inch sized hail.  This was accompanied by pea sized and marble sized hail as well.

Hail in MISSOULA, MONTANA
From 29-JUN-10 20:40:00 to 29-JUN-10 21:15:00 (MST-7)
Location: (MSO)MISSOULA INTL A
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

NWS employees measured one inch size hail at the weather forecast office.

Hail in MISSOULA, MONTANA
From 29-JUN-10 17:20:00 to 29-JUN-10 17:42:00 (MST-7)
Location: CONDON USFS ARPT
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail 1.25 inches in diameter was reported at Lindbergh Lake.  Small branches were stripped off pine trees and were covering the ground.

Thunderstorm Wind in RAVALLI, MONTANA
From 29-JUN-10 21:45:00 to 29-JUN-10 22:40:00 (MST-7)
Location: FLORENCE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Power was out in the Florence area as reported by an NWS employee.

Thunderstorm Wind in RAVALLI, MONTANA
From 29-JUN-10 22:00:00 to 29-JUN-10 22:40:00 (MST-7)
Location: FLORENCE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Power lines down near Highway 93 and Carlton Creek Road between Lolo and Florence.

Thunderstorm Wind in POWELL, MONTANA
From 29-JUN-10 14:50:00 to 29-JUN-10 14:58:00 (MST-7)
Location: OVANDO
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported estimated wind gusts of 60 MPH.  Smaller tree branches were down with the largest branch estimated at four inches in diameter.

Hail in MISSOULA, MONTANA
From 29-JUN-10 21:23:00 to 29-JUN-10 21:45:00 (MST-7)
Location: SEELEY LAKE ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A weather spotter reported  one inch diameter hail near Seeley Lake.