Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
December 20, 2020
Submitted:
December 21, 2020
Observer:
SAC - VandenBos (off duty)
Zone or Region:
Banner Summit
Location:
Copper (6,700-7-600', primarily NE-N)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Widespread
Collapsing? 
Widespread
No avalanche activity observed, but very little visibility.

Snow Stability

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

Bottom Line

New snow and warm temperatures are helping to establish a hefty slab on top of the weak snow underneath.

Media/Attachments

Previous cracking/collapsing along creek at 6,700' in Banner Summit Zone.

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Temperature:
Near freezing
Wind:
Moderate

Sunday afternoon driving obs, Hailey to Stanley: Mostly cloudy to overcast in Hailey, driving north, precipitation began around Baker Creek, where it was snowing fat, heavy flakes around 1300. By Owl Creek precip had turned to rain with moderate intensity. Rain transitioning to wet snow around Galena Lodge (7,300'). Snowing S1 up and over the pass and down to Headwaters parking, where precip decreased in intensity a bit. Driving down the valley light, wet snowfall transitioned to drizzly rain around 6,600' or so. North of Stanley, rain/snow line was at around 6,500-6,600' all the way to sunset. Above that, dense, wet snow was falling.

Snowpack Observations

HS=100cm at 7,500'. 45cm new snow from past week, difficult to be certain how much was from past 24 hours, but appeared to be between 20 and 30cm. Several layers of buried SH down 40-45cm, likely buried 12/11, 12/13, and 12/15?
-ECTP 1, 10, and 11, all down 45cm
-CPST 17/100 and 20/100, both to END, down 45cm
-PST 15/100 and 17/100, both to END, down 45cm

Snowpit at 7,500' on a NE facing slope below Copper Mountain in the Banner Summit Zone. HS=100cm

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): Dec 11, 2020 (FCsf)

Terrain Use

Avoided avalanche terrain at all scales, large and small