Pro Field Report

Basic Information

Observation Details

Observation Date:
February 1, 2023
Submitted:
February 1, 2023
Observer:
SAC - Davis
Zone or Region:
Banner Summit
Location:
Cape Horn Summit (All aspects, 6,700-8,400')

Signs of Unstable Snow

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

Snow Stability

Stability Rating: 
Very Good
Confidence in Rating: 
High
Stability Trend: 
Steady

Bottom Line

I observed a small wind slab avalanche that likely failed after the snowfall ended last weekend. It seems unlikely that the weekend storm formed slabs large enough to produce slides >D1.5. I targeted middle elevation, sheltered, shaded slopes and the early January weak layers were unremarkable. The snowpack below these layers was strong and unlikely to produce a slide in this location.

Media/Attachments

(1/5) presented as 2-3 mm SH (ECTNs). The overlying slab graded from F at the surface to 1F at the base. The snowpack below this layer was very strong (P).
(1/5) presented as 1-2 mm FC (ECTXs, CTNs). The overlying slab graded from F at the surface to 1F at the base. The snowpack below this layer was very strong (P). This pit was not dug to the ground.
(1/5) presented as 1-2 mm FC (ECTXs). The overlying slab graded from F at the surface to 1F at the base. The snowpack below this layer was very strong (P). This pit was not dug to the ground.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Sunny
Temperature:
20-30F
Wind:
Light , W
New/Recent Snowfall:
HST = 8 cm since (1/27)

Some thin clouds made for diffuse sun at times, but it was mostly sunny. Light W wind. Some sifting and flagging on Copper Mtn ridgeline, but it gave me the impression that it was mostly sublimating.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
1 Cape Horn Summit
E 7600 		D1 SS I-New/Old Interface N-Natural Very thin wind slab. It looked like it only involved the few inches of new snow since (1/27).
This thin wind slab released near Cape Horn Summit on an E aspect near 7600'.

Snowpack Observations

See photos

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: 40 cm
Weak Layer(s): Jan 5, 2023 (SH)
Comments: I dug on WNW, NE, and E aspects between 7,900 and 8,300' specifically looking for this layer. I found 2-3 mm SH in the WNW pit (ECTNs) and 1-2 mm FC in the others (ECTXs). Shaded where I looked.
Wind Slab
Isolated
Specific
Widespread
 Unknown
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Comments: I suspect that there may be some isolated wind slabs at upper elevation. Only about 6" of snow fell here over the weekend but the surfaces the slabs formed on are likely to be weak.

Terrain Use

Solo travel, I avoided avalanche terrain. I would have been comfortable skiing most slopes while avoiding any obvious drifting since (1/27) and any stiff harder slabs that may have formed in more alpine(ish) terrain last week.