Pro Field Report

Basic Information

Observation Details

Observation Date:
December 23, 2020
Submitted:
December 24, 2020
Observer:
SAC - VandenBos (off duty)
Zone or Region:
Sawtooth and Western Smoky Mtns
Location:
Alturas

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
Isolated

Snow Stability

Stability Rating: 
Fair
Confidence in Rating: 
Moderate
Stability Trend: 

Advanced Information

Weather Summary

Cloud Cover:
Clear
Temperature:
cold with a weak temperature inversion
Wind:
Moderate , NW

Cold all day. Suspect solar surfaces didn't melt except in steepest, sheltered terrain, but could imagine a little radiation recrystallization going on.

Avalanche Observations

Continuing to observe widespread avalanche activity related to the solstice storm. All crowns I observed were failing at interface between snow from past 10 days and the early season facets. Upper end of middle elevations with a bit of wind loading seemed to be the sweet spot for activity, did not observe widespread activity in the alpine but hard to say if that was because it was masked by snow and wind or if the facets weren't as well developed/preserved. In these areas, crowns were many hundreds of feet wide.

Snowpack Observations

Found IFrc extending from valley bottom up to about 8,700' or so. Slab of snow above early season facets is 30-35cm thick and still quite soft. Upper portion is 4F- to F+, lower half is F. Early season facets are F- at the top, F to F+ at base. With the exception of some moist snow at the upper end of the new slab and some moist facets near the ground the entire snowpack is dry. General sense is that the solstice rain and loading event did not significantly change the equation in this area. I'd expect to see activity on this interface continue with additional loading, the biggest change is that the overlying slab will be thicker than it was with this last storm.