Avalanche

JFS Canyon

Adam ClarkFlathead Range & Glacier NP
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Quick report

• One small slab avalanche just above the shed roof in Shed 6 located at 4600’ on an east aspect. o SS-N-R1-D1.5-O, crown was 5-10” thick (photo) and about 75’ wide. Debris ran about 100 vertical feet terminating above the shed. Failure layer was depth hoar at the ground. • Another small (D1) soft slab on a north-facing cut bank along Hwy 2 just east of Marias Pass (photo). Failure layer also appears to be some older snow and a persistent grain type. • No other avalanche activity observed. But visibility up into the higher terrain above the road was limited. • Snowfall last night totaled 4-6” on the Canyon floor with 5-10” above 6000’. • Another 2-3” accumulated on the Canyon floor today with 2-8” above 6000’. • Easterly winds intensified after the Arctic air arrived around daybreak. Blizzard conditions resulted and fresh wind slabs were forming at all elevations.

Weather

Cloud Cover
overcast
Wind Loading
intense
Snow Avail For Transport
large amounts

• The Arctic air arrived around daybreak today and temperatures rapidly dropped from the high-20s °F to the teens, then single digits, and now below 0°F. • Overcast skies today with moderate easterly winds and plenty of blowing and drifting snow. • Snowfall was very light for most of the day but picked up around sundown with rates of 1 to 2 inches per hour. • Air temperatures this evening above 6000’ range from 0°F at the western end of the Program to -18 °F at the eastern end.

Avalanche

Size
D1 R1
Type
SS
Count
2
Aspect
N
Elevation
5200 ft

Observed from Hwy around 0900. May have been triggered by plow debris?