Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
December 4, 2020
Submitted:
December 5, 2020
Observer:
Chris Lundy & Ben VandenBos
Zone or Region:
Galena Summit and Eastern Mtns
Location:
4th of July Lake (Primary snowpack obs from 9000-10700, N-NE)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced
Did see 2 small loose snow avalanches, unsure if they were within 48hrs

Snow Stability

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

Bottom Line

Relatively stable snowpack, although weak facets near the ground from October seem prevalent in this area on upper elevation, northerly slopes. Despite the lack of recent loading, this layer looks ugly enough that I wouldn't want to be on a steep, consequential slope where it exists. On slopes where the October snow doesn't exist, the snowpack is right side up and no slab/weak layer structure exists.

Media/Attachments

Small loose snow avalanche in the White Clouds

Advanced Information

Weather Summary

Cloud Cover:
Mostly Sunny
Temperature:
Strongly inverted
Wind:
Calm

Strong temp inversion in place with temps ~30 F warmer up high than at the highway.

Avalanche Observations

Two small loose snow (likely wet loose) avalanches observed above Washington Lake.

Snowpack Observations

Snow depth past the 4th of July trailhead averaged 40-75cm. Even in the shallower areas, the snowpack was maintaining at least enough strength to be supportable on skis or sled.

@9450', NW, 19*, HS 75cm: top 20cm faceting. 11/17 dust layer obvious but no crust present. Most significant finding was a ~7cm layer of 3-5mm DH atop a weak MFcr at the ground (60cm down). In addition to looking ugly, it produced a ECTP22 and PST29/100end.

Snowpit above 4th of July Lake showing weak October snow near the base of the snowpack. 9450', NW
Depth hoar near the ground found on a NW slope at 9450' in the White Clouds.

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
Weak Layer(s): Nov 7, 2020 (DH)

Terrain Use

We avoided steep, upper elevation, northerly facing terrain due to the existence of the weak October snow near the ground.