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Missoula Avalanche

Professional Observation

Basic Information

Observation Details

Observation Date:
December 5, 2022
Submitted:
December 5, 2022
Observer:
WCMAC - Arden Feldman
Zone or Region:
Rattlesnake
Location:
Snowbowl Backcountry

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Widespread
Collapsing? 
Widespread

Snow Stability

Stability Rating: 
Poor
Confidence in Rating: 
Moderate
Stability Trend: 
Steady

Bottom Line

Today we toured up Snowbowl to the Point 6 ridge area. There was light snowfall and overcast skies throughout the day. The temperature was cold. We measured -8 degrees celsius at 7400 ft. Winds were light to moderate out of the west. There was 2-4 inches of new snow overnight. Once we got off the beaten path, we observed widespread cracking and collapsing, and touchy avalanche conditions on facets buried 1.5 ft deep.

Media

Remotely triggered D1 persistent slab avalanche on a NE aspect at 7,400 ft.
Remotely triggered D1 persistent slab avalanche on a NE aspect at 7,400 ft.
Natural D2 persistent slab avalanche from late last week on a N aspect at 7,400 ft.
Widespread cracking and collapsing.

Advanced Information

Avalanche Observations

While walking along the ridgeline in the Little Alaska zone, we remotely triggered a small persistent slab avalanche on a NE aspect at 7400 ft. It broke 40 ft wide and 1.5 ft deep, failing on facets (SS-ASr-R1-D1-O). We also observed a larger natural persistent slab avalanche on a N aspect at 7,400 ft that likely failed during the storm late last week. It was 200 feet wide and 1-2 feet deep, failing on facets (SS-N-R2-D2-O).

Snowpack Observations

We dug a pit on an ESE aspect at 7500ft. We found a 1.5 ft deep slab from recent snowfall sitting on a weak layer of facets and surface hoar 2 ft above the ground. The slab failed easily in tests and propagated across the column (ECTP6). See attached snow profile for additional details. We also observed some small wind slab instabilities at upper elevations.

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