Pro Field Report
Basic Information
Observation Details
Observation Date:
December 28, 2020Submitted:
December 29, 2020Observer:
SAC - VandenBosZone or Region:
Sawtooth and Western Smoky MtnsLocation:
Smiley Creek (7,300-10,000, primarily N-NE-E-SE)Signs of Unstable Snow
Recent Avalanches?
YesCracking?
WidespreadCollapsing?
WidespreadSnow Stability
Stability Rating:
FairConfidence in Rating:
LowStability Trend:
ImprovingBottom Line
I experienced widespread cracking and collapsing of the snowpack on many slopes above about 8,000', some collapses extended for hundreds of feet. Had I been in steeper terrain, remotely triggering avalanches would have been a real possibility.
Advanced Information
Weather Summary
Cloud Cover:
Mostly SunnyTemperature:
teens F (estimated)Wind:
Light , ESteady wind blowing at upper end of light up high, calm elsewhere. Inverted temps, didn't feel like valley bottoms ever made it far above 0 F. Plenty of incoming solar radiation but not much melting of snow surfaces due to cold temperatures.
Avalanche Observations
Observed previously reported avalanches and glassed sizeable slide on south face of Williams in the Sawtooths.
Snowpack Observations
A healthy layer of 2-3mm surface hoar was present on all observed aspects without tree cover up to 9,000'. Temperature inversion (up to around 8,000') is having a significant affect on new snow from 12/26, producing ~6-8" of F- facets on top of the rain crust. This snow won't hold up well to rapid loading. Ski pen to ground in many places. Above this, HS=80-100cm, slab of snow since 12/11 is 35-50cm thick in sheltered locations. Standard and nonstandard snowpack tests are generating rough shears at 12/21 interface, but overlying slab is still too soft to say if this will be a significant problem going forward. As it stands, the late fall facet stack is near enough to the surface that it probably doesn't make much of a difference, yet.
At 8,600' on ENE:
HS=80, 12/11 down 40cm
ECTP 4 and 6 down 40cm on 12/11
CPST 17/100 and 20/100 to END on 12/11
PST 17/100 and 21/100 to END on 12/11
Slope collapsed twice before
Avalanche Problems
| Problem | Location | Distribution | Sensitivity | Size | Comments |
|---|---|---|---|---|---|
Persistent Slab
|
|
Weak Layer(s):
Dec 11, 2020 (FCsf)
Comments: Left out lower elevations in distribution due to lack of slab here. Sensitivity somewhere between reactive and stubborn |
Terrain Use
Avoided steep avalanche terrain where 12/11 persistent slab problem exists and terrain exposed to this problem from above.