The combination of cold, arctic air in place and the moisture from a Pacific low pressure system that tracked south and east of western Montana, created the perfect setup for heavy snow across western Montana. Widespread snowfall totals of near a foot were reported. The Potomac COOP reported a snowfall total of 18 inches on the 23rd, which is the highest, all-time 24 hour record since records began in 1964. Multiple stations reported their all-time coldest temperatures for the month of October few days later: 29 below zero in Potomac, 10 below at Seeley Lake and 7 below zero at Lindbergh Lake and Missoula.

Heavy Snow in KOOTENAI/CABINET REGION, MONTANA
From 23-OCT-20 09:00:00 to 24-OCT-20 08:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

The COOP station located 32 miles south of Libby recorded 13 inches of snow which would be the all-time one day record for the month of October. Other snow amounts include: 10 inches 2 miles southwest of Marion, 8 inches in Libby and 2 inches in Eureka. A person on Twitter remarked that Highway 2 became a sheet of ice between Libby and Kalispell.

Winter Weather in WEST GLACIER REGION, MONTANA
From 23-OCT-20 13:00:00 to 24-OCT-20 06:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

A employee from the Montana Department of Transportation reported a storm total snowfall between 4 and 6 inches from West Glacier to Devil's Creek along Highway 2.

Heavy Snow in LOWER CLARK FORK REGION, MONTANA
From 23-OCT-20 11:00:00 to 24-OCT-20 08:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Very heavy snowfall caused difficult travel through the region with several automobile accidents and slide-offs. Snow amounts in inches include: 17 Plains, 14 St. Regis, 12 Haugan, Superior, Alberton and Thompson Falls, 11.9 Evaro and 11 in White Pine. The unofficial amount of 12 inches in Haugan blew away the previous all-time one day total of 7 inches when compared with the COOP records.

Heavy Snow in BITTERROOT / SAPPHIRE MOUNTAINS, MONTANA
From 23-OCT-20 14:00:00 to 24-OCT-20 08:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Park/Forest Service

Lolo Pass received 15 inches of total snowfall from this event.  Other amounts in inches include: 14 Skalkaho Pass and Twelvemile Creek SNOTEL, 12 Lost Trail Pass, and 7 fourteen miles NE Sula.

Winter Storm in FLATHEAD/MISSION VALLEYS, MONTANA
From 23-OCT-20 13:45:00 to 24-OCT-20 08:00:00 (MST-7)
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Public

Very heavy snowfall fell in the Mission Valley with reports of strong gusty winds causing blowing and drifting issues around Flathead Lake. The peak wind at the Flathead Lake Bio station was 46 mph at 4 am, and around that same time a large tree fell over blocking highway 35 near milepost 20. Snow amounts in inches include: 14 Hot Springs, 13 Arlee, 12 St. Ignatius, 11 located 8 miles south of Wood's Bay, 10.5 Ronan, and 5 in Kalispell.

Heavy Snow in MISSOULA / BITTERROOT VALLEYS, MONTANA
From 23-OCT-20 14:00:00 to 24-OCT-20 07:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

A storm total of 13.8 inches fell in two days in Missoula, ranking second highest for a two day total in October, behind 15 inches that occurred on October 5-6, 1914. Other snowfall amounts in inches include: 12 Corvallis and Conner, 10.5 three miles NNE Lolo, 10 Lolo and Victor, 8 Hamilton, and 7 Stevensville.

Heavy Snow in POTOMAC / SEELEY LAKE REGION, MONTANA
From 23-OCT-20 15:00:00 to 24-OCT-20 09:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

The COOP observer reported a whopping 18 inches of total storm snowfall on the 24th. This COOP station has not been continuous, but during the period of 1965 to 2009, the highest 24 hour snowfall was 6.8 inches measured on October 21, 1975. The Seeley Lake COOP reported 11 inches on the 26th which makes it the highest 24 hour amount, topping the 9.6 inches observed on Oct. 31, 1942. Other snowfall amounts in inches include: 18 near Garnet Ghost Town, 17 Placid Lake, 15 five miles NW Seeley Lake, 14.3 Seeley Lake, and 10.9 Clinton.

Winter Storm in BUTTE / BLACKFOOT REGION, MONTANA
From 23-OCT-20 17:00:00 to 24-OCT-20 10:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Heavy snow combined with gusty easterly winds ranging between 15 and 35 mph caused blowing and drifting snow from Ovando, south along the Continental Divide towards Deer Lodge. Sixteen and a half inches fell at Avon, and this is not far below nearby Elliston's two day record of 18.9 inches that occurred Oct. 4-5, 1914 (Elliston did not submit an observation for this 2020 event). Additional snow totals in inches include: 16 Edwards Gulch near Drummond, 15 MacDonald Pass, 14.5 three miles SW Ovando, 11 Drummond, 8 Georgetown Lake, 6 Anaconda and seven miles south of Butte, and 5.8 Butte.