Observation: Catherine's Pass

Observation Date
12/18/2020
Observer Name
Cody Hughes
Region
Salt Lake » Little Cottonwood Canyon » Catherine's Pass
Location Name or Route
Catherine's Pass
Weather
Sky
Few
Wind Direction
North
Wind Speed
Calm
Weather Comments
A cold, calm, and beautiful day in the mountains.
Snow Characteristics
New Snow Depth
18"
New Snow Density
Low
Snow Surface Conditions
Powder
Snow Characteristics Comments
Right-side up powder on all slopes mid and upper elevations.
Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Cracking
Collapsing
Poor Snowpack Structure
Red Flags Comments
Our level one avalanche class observed many natural avalanches that most likely occurred yesterday and last night during high PI rates and heavy winds. Cracking and collapsing noted in the field today. Wind and heavy snow fall over the last 24 hours and a very poor structure observed in our snowpits.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments
The near-surface facets (NSF) that formed during the long stent of high pressure are now buried underneath roughly 18 to 32 inches of new snow in the upper Cottonwoods. Resting on top of these weak crystals lies a 4 finger slab (out of the wind zone) that is enough weight to get results in our snowpits. Natural activity on this layer during the storm was observed in our travels today. In the wind zone, on leeward slopes and terrain features, I would expect these avalanches to be more connected and more destructive. We dug on a west-facing slope to confirm our suspicion and verify the forecast of the PWL and the results can be seen in the video below.
Avalanche Problem #2
Problem
Wind Drifted Snow
Trend
Decreasing Danger
Problem #2 Comments
Winds were coming from all over the compass during the storm, and I suspect these freshly formed wind slabs to still be reactive to the weight of a skier or boarder. The issue is where the wind has blown snow on top of the slopes where the Persistent weak layer exists. This problem will not settle out quickly. The wind-driven snow has added a more stiff slab and is stressing this weak layer even further.
Video
Video:
West facing at 10,000 ft near Catherine's pass
HS 90 cm
Failure down 45 cm
Today's Observed Danger Rating
High
Tomorrows Estimated Danger Rating
High