Valanga

JFS Canyon

Adam ClarkFlathead Range & Glacier NP
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Quick report

Cracking
isolated
Collapsing
isolated

-The most recent melt-freeze crust from Monday (Feb. 26) on the Canyon floor thinned out and disappeared around 4800’. This now has about 2-4” of wet snow on top. • About a foot of recent snow above 5500’ with heavy wind loading from the SW winds. • Fresh wind slabs 1-4+ feet thick were observed above 6000’, primarily on N thru E aspects. Limited cracking from ski cuts in these slabs. • Observed one audible collapse on the SE ridge about 6200’ elevation. • We dug a snow pit within 50 yards of the recent hard slab crown in Shed 7 West (pit profile). We could not safely access the crown today. o Total snow depth was about 69” with the early Feb. facet layer buried about 35” down. o Stability tests results were variable with a mix of stable and unstable results. o We suspect the failure layer of the nearby avalanche was the layer of facets above the Feb. 3rd crust.

Weather

Cloud Cover
overcast
Wind Loading
intense
Rain Elevation
6000
Recent Snowfall
25
Snow Avail For Transport
large amounts

• Mostly overcast with occasional broken skies in the afternoon. • No precipitation all day until about sunrise when a rain/snow mix began on the Canyon floor. • Very windy, sustained moderate winds from the SW with strong to extreme gusts. • Wind loading was intense with several hundred-foot-long plumes of snow off the ridge crests above 6000’ at times. • Freezing levels climbed throughout the day reaching just above 6000’ by late afternoon.

Avalanche

Size
D2.5 R2
Type
HS
Count
5
Aspect
SE
Trigger
N
Elevation
6500 ft

• Several large hard slab avalanches observed today including. This all likely ran last night. • For many events it appeared that a cornice fall, and/or a wind slab near the ridge crest above may have triggered these larger avalanches. We suspect the failure layer to be the facets above the Feb. 3rd crust. -More details under the avalanche tabs