An overrunning system brought snow and a brief arctic intrusion along the Continental Divide. An upper level warm front brought heavy snowfall during the evening of the 11th from central Idaho to areas along and east of the Idaho and Montana border and created difficult travel.

Winter Weather in BITTERROOT / SAPPHIRE MOUNTAINS, MONTANA
From 11-JAN-18 01:00:00 to 12-JAN-18 08:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Park/Forest Service

Both Lolo and Lost Trail passes saw 14 inches of storm total snowfall during this event. Snowfall rates at Lolo Pass were heavy for several hours during the evening of the 11th.

Heavy Snow in LOWER CLARK FORK REGION, MONTANA
From 11-JAN-18 16:00:00 to 11-JAN-18 19:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

A period of intense heavy snow fell from Lookout Pass towards Haugan along Interstate 90 and also along portions of Highway 200 between the Idaho border and Trout Creek during the evening of the 11th. For observational snow amounts Lookout Pass ski resort reported 7 inches for the day through 7 pm and saw a three day total of 24 inches.

Winter Weather in KOOTENAI/CABINET REGION, MONTANA
From 11-JAN-18 15:00:00 to 12-JAN-18 08:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A period of moderate to heavy snow moved over the region by the evening of the 11th creating low visibility and slick roads. Total snowfall amounts ranged between 6 and 7 inches from Trout Creek to Bull Lake.

Winter Weather in WEST GLACIER REGION, MONTANA
From 10-JAN-18 12:00:00 to 12-JAN-18 11:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

An arctic cold front moved west along US-2 past Marias Pass and Essex by noon on the 10th causing wind gusts between 40 and 50 mph and periods of moderate to heavy snow, low visibility less than 500 feet at times, blowing and drifting snow. Snowfall amounts from this first part of the storm included 2 inches at Essex, 4.1 at West Glacier to 7 inches towards Marias Pass. Another 2 to 3 inches of snow fell between the 11th and 12th.

Winter Weather in FLATHEAD/MISSION VALLEYS, MONTANA
From 11-JAN-18 08:00:00 to 12-JAN-18 10:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Moderate snow fell across the region while blowing and drifting snow occurred in the Polson area due to gusty north winds off of Flathead Lake. Total Snowfall amounts included 4 to 6 inches in the Flathead Valley and closer to 7 inches in Polson. The Polson schools had a 2 hour delay on the 12th. A 82 year old woman died as a result of injuries sustained in a two-vehicle accident on Montana Highway 40 between Columbia Falls and Whitefish. Slippery road conditions were one of the suspected factors in the crash.

Winter Weather in POTOMAC / SEELEY LAKE REGION, MONTANA
From 11-JAN-18 18:00:00 to 12-JAN-18 11:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

The COOP observers at Lindbergh lake and Seeley Lake reported a total snowfall total of 19.1 and 17.0 inches respectively during this storm. Because of the heavy snowfall rates during the late evening hours of the 11th, tree damage and intermittent power outages were reported in these areas.