Pro Field Report

Basic Information

Observation Details

Observation Date:
December 13, 2020
Submitted:
December 14, 2020
Observer:
SAC - VandenBos, Peterson
Zone or Region:
Sawtooth and Western Smoky Mtns
Location:
Alturas Creek Drainage (7,000-9,500' primarily NE-N-NW)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced
Very isolated cracking in stiff drifts from wind last week.

Snow Stability

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

Bottom Line

Not enough new snow to change the stability picture, yet. With additional wind and snow, I expect to see thin, isolated slabs starting to form. These may be touchy due to the nature of the surfaces they are resting on.

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Temperature:
teens F (estimated)
Wind:
Moderate , SW

Light to moderate winds blowing out of the SW in exposed upper elevation terrain. Periods of up to S1 precip, mostly S-1. 1cm of new snow from 12/11, 3cm from 12/13. 4cm at highway level from 12/11, 5cm in stanley at 7pm.

Snowpack Observations

Rain crust from 11/17 is present up to around 8,000', fades away between 8,000 and 8,500'. At 9,000' there is no sensible crust present at 11/17 interface. Dug at 9,000' on N-facing slope, where HS =75cm. ECTN23 down 40cm on 11/17 interface (a few cm below the dustiness, as we've seen elsewhere) and ECTN27 down 65-70cm on 11/7 (top of October snow). Old snow is presenting locally as a 5 cm thick stack of dry, 2.5-5mm cupped and striated DH above a 1-4cm P+ MFcr. Continue to be worried about both of these interfaces moving forward, but we are currently lacking a slab. Snowpack is thinner than further north in Sawtooths and around Copper, which has helped to promote quite a bit of faceting in the lower half of the snowpack.

As observed further north, deep temperature inversions have produced a concerning combination of 20-30 cm of advanced facets resting on a rain crust at lower elevations. Higher up the rain crust isn't present but the faceting is still quite pronounced. We were able to trigger facet small facet sluffs at all elevations on slopes in the mid 30's.

Terrain Use

Continue to avoid large, open, shaded alpine terrain where October snow forms base of the snowpack.