Pro Field Report

Basic Information

Observation Details

Observation Date:
January 19, 2020
Submitted:
January 19, 2020
Observer:
SAC - Lundy (off duty)
Zone or Region:
Banner Summit
Location:
South of Copper Mtn

Signs of Unstable Snow

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

Bottom Line

This was a rec tour to check out a few of the large avalanches that released in the Banner Summit zone. These broke 5-6+’ deep on weak layers near the ground. Below average early season snowfall followed by last week’s major storm produced on of the most significant avalanche cycles in this zone in recent times. The same can be said for the northern and central Sawtooths.

Media/Attachments

Debris of D3 deep slab avalanche south of Copper Mountain.
Location of crown profile discussed in snowpack obs. 8700', E.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Sunny
Wind:
Light , SW

Low clouds lingered in Stanley until at least late morning. The sun and warm temps were definitely sufficient to affect solars, especially those exposed to afternoon sun.

Snowpack Observations

Snow depths ranged from 120cm at the highway to 180-230cm at upper elevations.

I did a quick crown profile in one of the large slides south of Copper. It was in a relatively sheltered portion of the crown, 8700’, E. HS was 185cm. The avalanche failed 160cm deep on facets 20-30cm above the ground. While many (or most) of the large slides that ran in this cycle were on north aspects that likely had October snow, I don’t believe this E aspect did. The basal facets were 3-4mm and not quite depth hoar. There was no crust adjacent to the facets.

Probing on a nearby shadier aspect, the depth was 230cm and I could feel a very prominent depth hoar later in the bottom 30-40cmbb

5-6' crown of very large deep slab avalanche that released south of Copper Mountain. The avalanche released on weak, sugary snow near the ground. 8700', E aspect.