Pro Field Report

Basic Information

Observation Details

Observation Date:
January 6, 2021
Submitted:
January 6, 2021
Observer:
SAC - Chris Lundy & Ben VandenBos
Zone or Region:
Banner Summit
Location:
Cape Horn Ridge (6700-8900', NE-E-SE-S)

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
None Experienced
Collapsing? 
Isolated
One very large and loud collapse occurred while stepping out of a snowpit (7700', E). Sounded like a muffled gunshot.

Snow Stability

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

Bottom Line

The recent storm has added even more load to the buried weak layer. The snowpack structure remains very poor, with a 3' thick, dense slab overlying a weak layer that shows little sign of improvement. Any triggered avalanche would be extremely dangerous.

Media/Attachments

Persistent slabs that released in Fir Creek in the Banner Summit zone during the last storm. 8400', E.
Persistent slabs that released near the head of Swamp Cr in the Banner Summit zone near the end of the recent storm. 9000', SE.
https://www.youtube.com/watch?time_continue=1&v=8ZI3NGbGxxc&feature=emb_logo

Advanced Information

Weather Summary

Cloud Cover:
Partly Cloudy
Wind:
Light , SW
New/Recent Snowfall:
Settled storm total from 1/4-5 seemed to be 35-40cm.

Storm snow was surprisingly settled - ski pen was only around 20cm on average. Clouds increased during the day, but overall less cloud cover than expected.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
3 Jan 5, 2021
(+/- 1 day) 		South of Copper
E 8700ft 		D1.5 SS-Soft Slab O-Old Snow N-Natural Report
2 Jan 5, 2021
(+/- 1 day) 		Fir Creek
E 8400ft 		D2 SS-Soft Slab O-Old Snow N-Natural
Persistent slabs that released in Fir Creek in the Banner Summit zone during the last storm. 8400', E.
Report
2 Jan 5, 2021
(+/- 1 day) 		Head of Swamp Creek
SE 9100ft 		D2 SS-Soft Slab O-Old Snow N-Natural
Persistent slabs that released near the head of Swamp Cr in the Banner Summit zone near the end of the recent storm. 9000', SE.
Report
South of Copper
Fir Creek
Head of Swamp Creek

Avalanche activity was not as widespread or dramatic as following the Solstice storm, but was still significant. There were a number of distinct persistent slab crowns, slides that released midstorm with obscured details, and evidence of shallower, storm-related avalanches.

Snowpack Observations

Persistent slab problem seems concerning at all elevations. Slab is thinner/softer down low but weak layer seems weaker. Slab gets thicker and denser as you gain elevation; the weak layer may gain some strength but the structure remains terrible. Trending towards a deep slab problem.

@7700', E: HS 125cm. Slab is 90cm thick and 1F at bottom over F/F+ 12/11 FC. ECTP23, 30; PST26/100end; CPST22/100end. When I stepped out of the pit, we had a huge and loud collapse - sounded like a muffled gunshot.

@8800', ENE: HS 135cm. Slab is 90cm thick and 1F at bottom over F+ 12/11 FC. Interestingly, the slab depth was only 15cm thicker than when I dug in the same spot on 1/4 - the storm must have caused some significant settlement. ECT did not fail within standard steps, but produced a ECTP with a hard hit.

Snowpit at 8800', E. 12/11 layer is beneath a dense, 90cm slab that is 1F hardness for the bottom half.

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: 70-90cm
Weak Layer(s): Dec 11, 2020 (FCsf)
Comments: Two different snowpits produced ECTPs and short PST cut lengths.

We did not observe a wind slab problem or any consistent/concerning shears above the 12/11 layer.

Terrain Use

We happily avoided avalanche terrain.