Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
January 23, 2023
Submitted:
January 23, 2023
Observer:
SAC - Chris Lundy
Zone or Region:
Banner Summit
Location:
Cape Horn (6700-8800', primarily NE-E)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced

Snow Stability

Stability Rating: 
Good
Confidence in Rating: 
Moderate
Stability Trend: 
Improving

Bottom Line

I found the primary weak layer of concern to be the surface hoar layer that was buried in early-January and is now 1.5-2' deep. I only found this layer in one snowpit, and it was showing signs of improvement. However, the variable and sporadic nature of surface hoar - and a somewhat recent skier triggered slide that I observed today - continues to give pause.

Advanced Information

Weather Summary

Cloud Cover:
Overcast
Wind:
Light , N

Temps felt colder than weather stations indicated - I would have guessed mid teens. Ridgetop winds were on the upper end of light gusting to moderate. Little snow being moved, and only small amounts remain available.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Jan 21, 2023
(+/- 3 days)
South of Boundary Creek Road
N 7250ft
D2 SS-Soft Slab O-Old Snow 1.5ft AS-Skier
u-Unintentional
Persistent slab avalanche apparently triggered by a skier on Banner Summit. Slab depth and terrain characteristics are consistent with early January surface hoar layer. 7250', NNW. Photo taken Jan 23rd.
Report
South of Boundary Creek Road

Snowpack Observations

Primary goal was to look at weak layers in the top 1m of the snowpack, particularly on shady slopes.

I only found the 1/5 SH in 1 of 3 pits. Where I found it was a very sheltered opening at middle elevations (8250, NE) - a place where I often find SH. In this location, the layer was very thin/compressed and most of the SH was in fragments. 2 ECTS: one ECTX, one ECTP with very hard force. Additional layers (likely 12/19 and 12/26) were present 60-90cm subsurface, but these produced no result and wouldn't shear when I tipped the block out.

I did two other pits around 8800', ENE. These were semi-sheltered slopes but fairly representative of upper elevation start zones. I did not find the 1/5 SH in either location - only small, indistinct FC. ECTX even with very hard hits. In one of these pits, I did see an old SH layer down 95cm that produced an ECTP with very hard force. I believe this is likely 12/8 but I couldn't say for sure. The SH xtals were 5-8mm but mostly laid over. Given the lack of reactivity in tests and that the bottom 50cm of the slab was P+ this layer didn't seem that concerning.

HS in these locations was 170-190cm.

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: 50
Weak Layer(s): Jan 5, 2023 (SH)
Comments: Rose shaded where observed. Layer was unreactive in tests but I'm calling it stubborn due to semi-recent triggered avalanche.

I only found small drifts from the recent N winds and these produced only minor cracking, although I wasn't in the best terrain for assessing wind slabs. I would anticipate there being a minor wind slab problem in the right terrain.

Terrain Use

I avoided avalanche terrain due to solo travel