Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
December 26, 2021
Submitted:
December 27, 2021
Observer:
SAC - VandenBos
Zone or Region:
Galena Summit and Eastern Mtns
Location:
Butterfield (6,700-8,400', N-NE-E-SE)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
None Experienced
Cracking in thin middle elevation wind drifts. Visibility was poor and I did not observe any avalanches.

Snow Stability

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

Bottom Line

The ongoing storm continues to push the snowpack to its breaking point. As the slab continues to grow and settle the likelihood of impacting the weak layer as a person decreases, but that's not much to hang your hat on.

Media/Attachments

https://www.instagram.com/tv/CX_FcxTFEC5

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Wind:
Light , W
New/Recent Snowfall:
40-50cm HN24 (?)

Afternoon tour. Snowing S-1 to S1 throughout tour. Light winds gusting moderate at lower and middle elevations, it sounded like it was blowing harder further up but I did not enter upper elevation terrain on this day. Difficult to tell how much it is actually snowing on each day, but based on tracks in previous skin tracks and texture/consistency of the snow, 40-50cm in the past 24 hours seems appropriate.

Snowpack Observations

In this area the slab that was built over the previous 2 weeks is now 130-140cm thick, HS=175-185cm. Upper 60cm are in the F- range, then grading pretty smoothly down to P- at the base of the slab. Continuing to get propagating results in ECTs (ECTP 22 and 24) and very short cut lengths in CPSTs (CPST 28/140, and 36/140, both END). Results are from a pit at 8,200' on N facing slope. See video attached below.

I've been seeing some consistent dirty shears in the upper snowpack but nothing terribly alarming (yet). Most obvious seems to be about 50 cm down, roughly corresponding to either a change in PP or perhaps a quick hit of FCsf from the window of clearing on 12/24? Impossible to distinguish visually, mostly just apparent by how the snow behaves in shovel shears. Continuing to monitor.

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
Weak Layer(s): Dec 11, 2021 (FC)
Comments: Rose shaded based on where problem is known to exist, based on previous observations.

I did not directly encounter either a storm slab or wind slab problem in the terrain I traveled in. But, based on remote observations I'm sure a wind slab problem exists in upper elevation terrain and likely at the upper end of middle elevations as well.

As with many places we are trending towards a deep slab instability here, but given the rate of ongoing loading and slab creation, it is a bit hard to want to describe it as that until after the dust settles a bit.

Terrain Use

Continuing to avoid avalanche terrain where 12/11 is present as anything other than the ground.