Professional Observation
Basic Information
Observation Details
Observation Date:
December 22, 2020Submitted:
December 23, 2020Observer:
WAC - Caleb MerrillZone or Region:
ElkhornsLocation:
Angel BasinSigns of Unstable Snow
Recent Avalanches?
None ObservedCracking?
None ExperiencedCollapsing?
None ExperiencedBottom Line
At this location, the Rain Crust that developed during the winter solstice was supportive to the weight of a person. As we dug deeper in the snowpack, there was clearly a cohesive (strong) slab of snow above a weak crust/sugar snow combination (from 12/9) that was found 20-30" below the snow surface. This layer produced sudden, energetic, and propagating results in our snowpack tests.
Advanced Information
Weather Summary
Cloud Cover:
ObscuredWind:
Moderate , NEDuring our tour, we experienced new snowfall at light to moderate rates. Graupel snow- that dense form of snow that looks like small styrofoam pellets was observed on the snow surface. Temperatures were in the teens, and light to moderate winds were blowing the new snow around on the firm crust surface.
Snowpack Observations
We observed a firm crust surface with areas of wind drifted new snow up to 6" deep. At this time, and at this location, this "Solstice Rain Crust" was a series of 3 pencil hard crusts with softer snow sandwiched between. Perhaps this formed due to dynamic freezing levels during the rain/snow event at this elevation. This crust is able to support the weight of a person at this time. In areas where this crust is thinner, or as it breaks down over time, the weight of a person and/or machine may be able to more easily impact weaker sugar snow deeper in the snowpack. Snowpack test results produced easy, clean, and energetic shears within these facets that were found below a crust from December 9th. Compression Test Results: CTE SC down 50 cm below 12/9 crust. PST results 30/100 (END) down 50cm on 20201209.
Avalanche Problems
| Problem | Location | Distribution | Sensitivity | Size | Comments |
|---|---|---|---|---|---|
Persistent Slab
|
|
Layer Depth/Date: December 9th Crust/20-30" (50-70cm) from surface |
Terrain Use
We stayed in simple terrain void of large avalanche paths and terrain traps.
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