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Missoula Avalanche

Professional Observation

Basic Information

Observation Details

Observation Date:
January 5, 2022
Submitted:
January 6, 2022
Observer:
WCMAC - George D'Angelo
Zone or Region:
Southern Bitterroots
Location:
Lost Trail Backcountry

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
None Experienced
Isolated Cracking of 1-2' wind slabs at ridgelines.

Snow Stability

Stability Rating: 
Fair
Confidence in Rating: 
High
Stability Trend: 
Worsening

Bottom Line

Found a primarily right-side up snowpack above the faceted layer near the bottom of the snowpack. The cold temps have kept a storm slab from forming so far, but I expect that to change with warming temps and more snowfall Thursday onward. Keep an eye on the warming temps tomorrow (Thursday) and how that will help consolidate the existing light snow into a more cohesive storm slab. Reactive windslabs are present in wind-loaded areas, primarily at and near ridgelines.

Advanced Information

Weather Summary

Cloud Cover:
Overcast
Temperature:
11*F
Wind:
Moderate , W

Cold temps and moderate westerly winds kept wind slabs actively forming and good surface riding conditions on wind-sheltered slopes.

Snowpack Observations

Height of Snow - ~6' (190cm) NE aspect @ 8000' :Propagation Saw Test PST 55/135 end on Depth Hoar 2- 8mm. Extended Column Test ECTN down 14" on Precipitation Particles (Stellar Dendrites) 2mm. Compression Test Moderate, Sudden Planar down 14" (35cm) on Preserved Precipitation Particles. Compression Test Hard Resistant Planar down 22" (55cm) on Near Surface Facets.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Deep Persistent Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
Layer Depth/Date: 4-5ft (120-150cm)
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: 1-2ft (30-60cm)

The storm slab problem likely will be here Thursday with warming temps and increasing snowfall.

Terrain Use

We kept it to mellow ~30 degree slopes on any northerly facing terrain and found great surface conditions on all aspects in wind-sheltered terrain.

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