Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
January 18, 2021
Submitted:
January 19, 2021
Observer:
SAC - VandenBos
Zone or Region:
Banner Summit
Location:
Langer Peak (6,500-9,000')

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced
Stability somewhere between fair and good.

Snow Stability

Stability Rating: 
Fair
Confidence in Rating: 
Stability Trend: 

Bottom Line

Weak snow from December is buried 3.5+ feet deep in this zone, but weak layer is still producing unstable results. Facets are very slowly healing, but combination of terrible structure (strong snow over weak snow), unstable snowpack tests, and large recent avalanches is enough to keep me out of consequential avalanche terrain in this zone.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Cloudy
Wind:
Light , N

Broken to overcast skies, very light precip falling occasionally with no accumulation. Light to moderate winds blowing out of the north, not transporting snow.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Jan 13, 2021
(+/- 1 day)
Langer Peak
NE ft
D2 O-Old Snow N-Natural Report
1 Jan 13, 2021
(+/- 1 day)
Ruffneck Peak
N 9200ft
D3 O-Old Snow N-Natural
This very large avalanche occured in our Banner Summit Zone, likely during last week's storm. Based on the depth and appearance of the crown it probably failed on facets buried near the base of the snowpack.
Report
Langer Peak
Ruffneck Peak

Observed evidence of several avalanches that failed on deeply buried weak layers during last weeks storm. I was unable to determine what layer these failed on due to the amount of snowfall and wind loading that occurred after the avalanches happened.

Snowpack Observations

Slab over 12/11 is 1m thick in this area, with the majority of the slab being 1F to P. 12/11 facets/depth hoar are showing signs of improvement, but this is happening quite slowly. Where I dug (E at 7,600' HS=130-140cm) the facets were 4F- at the top of the interval and quickly graded to 4F. Density differential between slab and weak layer is still striking. I was unable to initiate fractures at this interface in standard loading steps with an ECT, continued bashing on the column produced fractures that did not propagate. However, PST and CPST produced repeated short cut lengths and propagation to end. CPST 29 and 30/120 END, PST 28 and 35/120 END, all down 100cm on 12/11 interface.

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, 2020 (FCsf)
Comments: Location rose reflects where problem is suspected to be at its worst, but the weak snow from December is widespread. Sensitivity between stubborn and unreactive

Terrain Use

Avoided avalanche terrain. Would have felt comfortable in simple, small avalanche terrain in the low 30s.