Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
January 3, 2020
Submitted:
January 3, 2020
Observer:
Lundy
Zone or Region:
Banner Summit
Location:
Cape Horn

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
Isolated
Got a few small to medium collapses on a mid elevation ridgeline. The snowpack consisted of soft wind slab over shallow, weak snow.

Snow Stability

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

Bottom Line

Similar to yesterday's observation from Frenchmans, the 12/31 storm did not add enough load for widespread avalanche activity. Still, the added load is keeping buried weak layers reactive in tests and triggering a slide remains possible.

Media/Attachments

View of the Cape Horn ridge. Would have expected more avalanche activity in this area, but then again, much of this ran in mid December.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Cloudy
Wind:
Light , W

Skies began OVC, then decreased to SCT by early afternoon, then increased back to BKN. The hour or two of SCT clouds allowed some solar radiation to affect sunny slopes. Winds were occasionally MOD, but not much snow was moving. Temps overall were cooler than expected.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
Several Steep slopes at a variety of aspects and elevations
D1 SS I-New/Old Interface 30cm N-Natural Numerous small storm slabs on steep slopes, including in sheltered treed terrain. None
2 Cape Horn Ridge
NE 8900
D1 HS I-New/Old Interface N-Natural Two wind slabs that released and didn't go far.
1 Top of Copper Mtn
NE 8900
D2 SS U-Unknown Assume a natural but can't say for certain given skier traffic on Copper. Suspect this was a wind slab, but can't gauge from the photo whether it broke into deeper weak layers.
Avalanche on the NE side of Copper Mountain that ran during the New Year's storm. It may have broke on buried persistent weak layers.

All noted avalanches ran during or just after the 12/31 storm. Not as much avalanche activity as expected, although a lot of the steep, shady slopes in this area ran in mid December.

Snowpack Observations

Snowpack observations were from 6700 to 9000', SW-S-SE-E-NE.

Average depth ranged from 40-50cm at the highway to ~100cm on upper elevation shady. Solars at all elevations were quite thin. 25-30cm of new snow from the 12/31 storm, higher density than what I found in Frenchmans and what's been reported on Galena. No issues at the 12/31 I.F. were observed in handpits or snowpits.

Low elevations and mid elevation solars are thin - the 12/31 storm fell onto a shallow/weak snowpack. Generally no issues in these areas unless you find an area that's been windloaded. We got a couple small to medium collapses on a mid elevation open ridge.

@8150, SE: HS=80cm. 12/7 SH barely visible 67cm down - ECTP22.

@8800, ENE: HS=105cm. 12/7 SH down 60cm - ECTX, PST32/100end. The SH layer seems to be thinning and looking at it closely it seemed to be integrating into layers above and below. 11/26 FC/crust/DH down 75cm - ECTX, PST40/100end.

Stomped on some cornices and wind slabs with no results.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
None Specified
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
Layer Depth/Date: 60-70cm: 12/7, 70-80cm: 11/26
Comments: The wind slab problem seems to have run it's course in this area.

Terrain Use

Avoided avalanche terrain, but would have felt comfortable stepping out into low 30 degree terrain without serious consequences.