Professional Observation
Basic Information
Observation Details
Observation Date:
January 1, 2021 - January 1, 2021Submitted:
January 2, 2021Observer:
WAC - Michael HatchZone or Region:
ElkhornsLocation:
East Shoulder of Lee's Peak - 8400'Signs of Unstable Snow
Recent Avalanches?
None ObservedCracking?
None ExperiencedCollapsing?
None ExperiencedSnow Stability
Stability Rating:
FairConfidence in Rating:
HighStability Trend:
WorseningBottom Line
The existing snowpack in the Northern Elkhorns exhibits weak strength and poor structure. The bottom 2' of the snowpack is composed of rounding facets (sugar snow) and a facet/crust combo about 18" from the surface demonstrated propagation propensity. The addition of 1-2' of new snow in the next 24-48 hours will stress the existing weak snowpack and likely lead to widespread storm slab instability.
Advanced Information
Weather Summary
Cloud Cover:
OvercastTemperature:
26Wind:
Light , SWThe weather was fairly mild through the early afternoon with temps in the mid-20's and light SW winds. Overnight the area had received about 15cm (6") of new snow. In the late afternoon the SW wind began to increase to moderate intensity (15-25mph) as the storm front rolled into the area.
Snowpack Observations
As mentioned above the overall snowpack structure is weak with numerous persistent weak layers existing throughout the snowpack. The most reactive layer in our snowpack tests was at a facet/crust combo about 50cm down or 18" from the surface. This crust is what we are calling the Solstice Rain Crust (SRC). It was formed during the warm front passage on 12/21 that brought rain up to at least 8500' in the Elkhorns. This is where we found a propensity for propagation in our tests - ECTP26 - where it failed below the SRC on 2mm facets.
Below the stout Solstice crust is a melt-freeze jarble consisting of about three facet/crust combos likely the result of a fluctuating rain line during the warm front passage. Below the jarble is about 2' of basal facets that are slowly rounding and gaining strength.
Avalanche Problems
| Problem | Location | Distribution | Sensitivity | Size | Comments |
|---|---|---|---|---|---|
Persistent Slab
|
|
Layer Depth/Date: 50cm/1-1-21 |
|||
| None Specified |
|
Terrain Use
Although the new snow totals (6") were not at threshold levels to cause widespread storm slab instability the persistent weak layers (especially the facet/crust combo down 18") demonstrated continued ability to propagate a fracture once initiated. We kept our slope angles below 35 degrees due to the uncertainty of reactivity of this PWL to the weight of a skier or rider. This layer will become increasingly reactive with the addition of 1-2' of new snow in the forecast.
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