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Missoula Avalanche

Professional Observation

Basic Information

Observation Details

Observation Date:
November 30, 2022
Submitted:
November 30, 2022
Observer:
WCMAC - Cam Mackenzie, Arden Feldman, Jeff Carty
Zone or Region:
Seeley Swan
Location:
Pyramid Peak

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced

Snow Stability

Stability Rating: 
Fair
Confidence in Rating: 
Low
Stability Trend: 

Bottom Line

First time into this terrain for the season. Coverage is still low, but avalanches are possible with the new snow tonight.

Media

NW Aspect, 6200', Pyramid Peak

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Temperature:
-3
Wind:
Light

Light snow during tour. 1cm new snow from start to finish of field work.

Snowpack Observations

This was the first time into this terrain for the season for WCMAC forecasters. Overall, the snowpack is shallow with average snow depths at 6200' at 50cm (20 inches). We were able to drive to 5200' at the Pyramid Pass trailhead, but I suspect with tonights snow this will no longer be possible.
Below 6000' on southerly aspects, the snowpack had only a few inches of snow on top of a supportable crust. Above 6000', the crust disappeared and the snowpack was primarily faceted with a shallow soft slab on top. The spatial variability of this facet/soft slab combination is uncertain as visibility was poor and we were unable to cover much of the terrain in the forecast zone.
As we move into the next storm, be suspicious of slopes holding old snow as they are most likely to harbor weak layers.

Avalanche Problems

First time into new terrain for the season. Avoided avalanche terrain as even though there was most likely not enough snow for avalanches, more data is needed for higher confidence in terrain choice.

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