Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
December 5, 2022
Submitted:
December 5, 2022
Observer:
SAC - Chris & Sara Lundy
Zone or Region:
Banner Summit
Location:
Cape Horn (6700-8800', N-E-S)

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
Widespread
We had widespread small to large collapses from the valley floor to our high point. Some shook snow off trees 20-30' away.

Snow Stability

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

Media/Attachments

Two skiers jumped simultaneously near the top of the slope, causing a large collapse that triggered the avalanche. The avalanche failed 3' thick on a thin layer of facets that were buried in late-November.
Natural avalanche on Cape Horn mountain that likely released Dec 1 or 2. It failed 2.5-3' thick on weak facets buried in late November.
https://www.youtube.com/watch?v=AsEbJcliMt4

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Wind:
Light , SW
New/Recent Snowfall:
~20cm from past 24hrs

Wind occasionally gusted to M but there was little snow being transported.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Dec 5, 2022
(Exact)
Cape Horn
NE 8700ft
D2 SS-Soft Slab O-Old Snow 3ft AS-Skier
r-Remote
Two skiers jumped simultaneously near the top of the slope, causing a large collapse that triggered the avalanche. The avalanche failed 3' thick on a thin layer of facets that were buried in late-November.
Report
Link
1 Dec 2, 2022
(+/- 1 day)
Cape Horn
E 8750ft
D2 SS-Soft Slab O-Old Snow 3ft N-Natural
Natural avalanche on Cape Horn mountain that likely released Dec 1 or 2. It failed 2.5-3' thick on weak facets buried in late November.
Report
Cape Horn
Cape Horn

Visibility was poor - I wouldn't have been able to see avalanche activity on the drive or across the highway on the north side of Copper.

Snowpack Observations

Slab was thicker and meatier than what is being observed on Galena Summit and south. Starting at 6700', the slab was ~60cm thick and 4F at the base. This increased to an 85cm thick slab that is 1F at the base at upper elevations. Overall HS ranged from 100-150cm.

The 11/27 weak layer presented as: ~30cm of F FC at lower elevations (thick layer of basal FC), a 3cm thick MFcr atop 20-30cm of F FC on mid elevation solars, to a fairly thin layer of F FC atop 40cm of 4F rounding/moist FC (October snow) at upper elevations. We received collapsing on all aspects we traveled on, but the structure and collapsing was most widespread on shady slopes.

A two person simul-stomp on a low-angle ridge triggered a D2 avalanche on the steep slope below. This was a fairly small slope, but the avalanche broke nearly 3' deep the full width of the slope - see avavalanche occurrence report.

A snowpit @8800', E, above a few day old slide looked very similar to the crown profile of the triggered slide. I had ECTX x2 which was surprising, but the pit location likely collapsed at the same time as the avalanche below the site.

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: 60-85
Weak Layer(s): Nov 27, 2022 (FC)
Comments: Triggered avalanche, widespread collapsing

Terrain Use

We avoided avalanche terrian