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Missoula Avalanche

Professional Observation

Basic Information

Observation Details

Observation Date:
March 6, 2022
Submitted:
March 7, 2022
Observer:
WCMAC - Jane Quinn
Zone or Region:
Southern Bitterroots
Location:
Mt. Fuji, Lolo Pass

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
None Experienced
Isolated pockets of wind slab 3 - 4" thick on East aspects on our ascent up Mt. Fuji

Snow Stability

Stability Rating: 
Good
Confidence in Rating: 
High
Stability Trend: 
Steady

Bottom Line

The three inches of "dust on crust" served to keep us just afloat on our descent. However, the melt-freeze crust below the surface could serve as a slick interface if we have a significant amount of accumulation on top of it that does not bond well. The persistent layer buried around 65 cm (26") appeared to be stubborn in our snowpit tests.

Media

Advanced Information

Weather Summary

Cloud Cover:
Mostly Cloudy
Temperature:
22 F
Wind:
Moderate , N

Precipitation was intermittent throughout the day, ranging in both rate and type from light to moderate and from snow crystals to graupel. As we ascended, winds increased to moderate and blowing snow was observed. There was not much loose snow available for transport but we did see the beginnings of wind slab formation.

Snowpack Observations

Skin track isolation tests revealed a 3" - 4" wind slab that was easy to trigger on the melt-freeze crust below.
CT24 Resistant Planar down 65 cm (26")
ETPN29 down 65 cm (26")

The melt-freeze crust measured around 15 cm (6"), which is a relatively skier-impenetrable surface when frozen.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Wind Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
Layer Depth/Date: 3-4" 03/06/22
Skin track isolation tests revealed a 3" - 4" wind slab that was easy to trigger on the melt-freeze crust below.

Terrain Use

We decided to stick to terrain 35 degrees and below and to focus on the learning outcomes of the field day.

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