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Observation: Bear Trap

Observation Date
12/21/2015
Observer Name
Patrick Fink
Region
Salt Lake » Big Cottonwood Canyon » Bear Trap
Location Name or Route
Bear Trap West
Weather
Sky
Broken
Precipitation
Moderate Snowfall
Wind Direction
Southwest
Wind Speed
Moderate
Weather Comments
Calm and sunny at times around 10-11 am, becoming overcast and gusty with the arrival of the storm. Winds were moderate to strong at ridgetop with active transport onto NE'ly slopes. Precipitation was rimed broken dendrites turning into yet more grauppel as the winds picked up.
Snow Characteristics
New Snow Depth
4"
New Snow Density
Low
Snow Surface Conditions
Powder
Dense Loose
Rain-Rime Crust
Snow Characteristics Comments
In sheltered areas, there were 4-5" of new low density snow. East facing aspects had only dense soft snow from the prior storm overlying the rain crust. Westerly aspects had significantly more (1-2') snow on top of the crust. This made for good riding characteristics.
Red Flags
Red Flags
Poor Snowpack Structure
Red Flags Comments
The structure remains the big problem. We stayed conservative and didn't ski over 30 degrees, but my impression is that today's snowpack was largely a Moderate Danger snowpack, with weak layer adjusted to the load from the prior storm. Still, it is so reactive in testing that this next storm should make things significantly spicier.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Increasing Danger
Problem #1 Comments
Switching from calling it a persistent slab to a deep slab with the anticipated snow. It's the same dragon-- basal facets underneath a rain crust. On an E-NE facing slope around 9500', the snowpack was about 60 cm in depth, with 15 cm of facets at the ground. Compression tests yielded progressive compression within the new snow and CT14Q2 sudden planar fractures at the top of the facets. In discussion with another party, they found that this failure was propagating readily in ECTs.
Avalanche Problem #2
Problem
Wind Drifted Snow
Trend
Increasing Danger
Problem #2 Comments
The wind with the incoming storm front really started whipping snow around. In the right places, this will mean hard little wind slabs which, if triggered, could be just what you need to start a slide that steps down to near the ground.
Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
High