Observation: Shingle Mill

Observation Date
12/23/2021
Observer Name
Mark Staples
Region
Uintas » Shingle Mill
Location Name or Route
Shingle Mill Flat
Weather
Sky
Obscured
Wind Direction
South
Wind Speed
Moderate
Weather Comments
Warm south winds and damp conditions have made the snow surface damp in lower elevation areas. At upper elevations, the snow surface is just dense, settled powder or "wind board". It seems that all of the near-surface facets and surface hoar are long gone.
Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Cracking
Collapsing
Poor Snowpack Structure
Red Flags Comments
All the boxes are checked, or they will be soon enough as the Christmas storm materializes
Avalanche Problem #1
Problem
Persistent Weak Layer
Problem #1 Comments
No surprise here. The soft slab on top of the PWL of facets from Oct/Nov is growing larger. I was able to remotely trigger this avalanche today. Any slope facing NW, N, & NE is an obvious place to find this problem. However, I wanted to check out west facing slopes, and sure enough - it's there. See photo below.
Comments
Similar layering exists on west facing slopes - mainly ones not stripped by winds from the west. The main difference is that the layer of weak facets seems to be a little thinner and a little closer to the ground. In the photo below you can see what remains of several decomposing crusts layered with the facets. Those crust have been "chewed up" by the faceting process and are now soft and fragile.
I did an extended column test, and it propagated across the whole column after 10 taps from the wrist (ECTP10 - a bad test result).
At low elevation (7600 ft) north facing slopes, there is roughly a foot of snow with a layer of facets at the ground about 2 inches thick. This layer will likely be interrupted by ground roughness (aka -rocks, stumps, etc.) and not be a major issue. In isolated places with a very smooth, grassy slope underneath, it could be a problem.
LOOKING AHEAD - There will be two major weak layers in the snowpack. One is the facets near the ground. The other will be layers within the new snow. These layers may be a density change or a crystal change in the new snow. Fortunatley this weak layer will only last 24-48 hours. Unfortunatley the facets near the ground will be an issue for weeks ahead.
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
High
Coordinates