A low amplitude upper ridge built into the region between Saturday Nov. 9th and Monday Nov. 11th. A plume of subtropical moisture brought steady precipitation and pushed  freezing levels up to 8,000 ft. across northwest Montana. A modified arctic air mass dropped out of Alberta, Canada during the early morning hours of Sunday Nov. 10th and it had just enough energy to push westward over the Continental Divide affecting the US-2 corridor from West Glacier to Marias Pass. Over a foot of snow was reported in these areas causing high impacts to travel.

Heavy Snow in WEST GLACIER REGION, MONTANA
From 10-NOV-13 00:12:00 to 11-NOV-13 05:12:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported that road conditions were terrible at 7:22 am MST Nov. 10th from West Glacier to Columbia Falls on US-2. The West Glacier COOP reported a storm total snowfall of 12 from Nov. 10-11 with 0.97 of precipitation. They also reported 0.67 of precipitation on Nov. 10th which was the 2nd highest amount since 1949. Other storm total snowfall amounts include: 7 Hungry Horse, 8-10 in Polebridge, and 7 Noisy Basin SNOTEL in the Swan Range at 6,040 ft.

Winter Weather in KOOTENAI/CABINET REGION, MONTANA
From 10-NOV-13 00:00:00 to 11-NOV-13 00:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

The Olney COOP observer reported 3 of snow between Nov. 10-11 with 0.58 of precipitation. The COOP observer located 9 mi. north-northeast of Yaak reported 2.2 of snowfall with 0.24 of precipitation on Nov. 10th. There were reports of slushy conditions in Libby, Eureka, and Troy during the morning of Nov. 10th.

Winter Weather in FLATHEAD/MISSION VALLEYS, MONTANA
From 10-NOV-13 00:00:00 to 10-NOV-13 10:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A weather spotter reported terrible road conditions on US-2 from West Glacier to Columbia Falls at 7:22 am MST on Nov. 10th. They reported light steady snow with up to 3.3 of snowfall through 10 am MST. The Glacier Park International Airport reported snowfall from midnight through 8:14 am MST on Nov. 10th with only 0.5 of accumulation. Glacier Park International Airport also reported 0.77 of precipitation on Nov. 10th which was the 2nd highest amount for the day.

Heavy Snow in WEST GLACIER REGION, MONTANA
From 10-NOV-13 03:00:00 to 11-NOV-13 02:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A person from the public in Essex reported 12 of snow as of 9:20 pm MST on Nov. 10th. They reported that US-2 was so bad that their boss had advised them not to travel. Earlier in the day they reported that roads were slick due to a layer of ice under the snow. The Pike Creek SNOTEL located 1.6 miles southeast of Marias Pass reported a total of 8 hours of heavy snow between 4 am and 5 pm MST on the 5th with a storm total snowfall of 11. The arctic front pushed through Marias Pass by 5:30 am MST on Nov. 10th which contributed to the heavy snowfall rates. The Shed 4 weather station (4,520 ft.) located 6 mi. southwest of Marias Pass measured 14.8 of snow with 0.75 of precipitation. The Summit HADS located at Marias Pass measured 0.60 of precipitation which could equate to 12 to 14 of snow(using a 20 to 1 snow to liquid ratio which matches Shed 4 observations).