Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
January 21, 2020
Submitted:
January 21, 2020
Observer:
SAC - Davis, Taylor
Zone or Region:
Banner Summit
Location:
Cape Horn Mountain

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
None Experienced
Cracking in fresh wind drifts 8-10" thick at middle elevation.

Snow Stability

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

Bottom Line

I found actively forming fresh wind drifts along exposed middle elevation terrain. These drifts cracked and released very small slabs below cornices. I did not experience any other obvious signs of instability.

Media/Attachments

Cracking and small releases below actively forming drifts and cornices in exposed middle elevation terrain. Banner Summit Zone, Cape Horn Mountain, north aspect at 8,200'.

Advanced Information

Weather Summary

Cloud Cover:
Overcast
Wind:
Moderate , S

Large flakes and light snow early in the day. Wind picked up midday and snow flurries increased as well. It was a little hard to tell new snow amounts due to the wind but 2" seems reasonable. Generally, the Sawtooths were also mostly cloudy but it seemed that the snow appeared to hang more at the crest.

Avalanche Observations

Small pockets of tapered, fresh wind slab below cornices. Hard to really call them an avalanche.

Snowpack Observations

@8000, S, HS=105cm:
No real standout upper or midpack layers of note in this location. The upper and mid-snowpack was right-side-up with F hardness at the surface steadily increasing to 1F+ until 40 cm off the ground. Beneath that, I found 4F and F+ basal facets with a weak, deteriorating crust mixed in. This layer produced ECTP18 and PST 43/100 end, down 95 cm and the failure occurred both above and below the crust. Other results: ECTX, ECTN down 25.

@8200, N, HS=130cm:
A quick look on a sheltered slope with limited open sky view also showed no obvious upper or midpack layers of concern. The basal facet layer was twice as thick (~40 cm) and the crust within was a bit stiffer but still crumbly and weak. No formal tests.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
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: 70-130 cm (@ middle elevation)
Comments: Basal facets produced ECTP18, PST 43/100 end
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: 10-25 cm (@ middle elevation)
Comments: Isolated at exposed middle but I assume it was getting to be a problem in specific upper elevation locations by the end of the day.

Terrain Use

We did not enter avalanche terrain.