Observation: Alta Periphery

Observation Date
11/17/2013
Observer Name
Bruce Tremper
Region
Salt Lake » Little Cottonwood Canyon » Alta Periphery
Location Name or Route
Rocky Point - shoulder of Sunset Peak
Weather
Sky
Clear
Wind Speed
Light
Snow Characteristics
New Snow Depth
12"
New Snow Density
Medium
Snow Surface Conditions
Dense Loose
Wind Crust
Snow Characteristics Comments

About a foot or more of new snow fell yesterday but it was fairly dense and the strong west wind created dense, windslab conditions on most slopes. The new snow was disappointingly stiff and upside down in many areas.

There is a total of about 2.5 feet of snow on the upper elevation, shady slopes but there was almost no snow on the south facing and west facing slopes where many rocks and other obstacles lurk beneath the new snow. It's the kind of conditions that force people to head to the exact same slopes most prone to avalanches because they also have the best snow for skiing and boarding.

Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Cracking
Collapsing
Rapid Warming
Poor Snowpack Structure
Red Flags Comments
Yup, checked all the boxes. It was the perfect setup for avalanches on steep slopes with a pre-existing, buried layers of faceted snow and depth hoar.
Avalanche Problem #1
Problem
New Snow
Problem #1 Comments

The main problem was where dense, wind drifted snow overloaded buried layers of faceted snow--both near-surface facets in the middle of the snowpack and very weak depth hoar on the bottom of the snowpack.

Comments

Here is a short video of a remotely-triggered avalanche by some skiers in another party that triggered the slide earlier in the day. We did not see it occur but I investigated the slide later in the day. Note: this is a different avalanche than the one reported by Evelyn, which caught a skier. This one is about 150 yards away but exactly similar aspect, elevation, steepness and snow structure.

Video

Photo of the remotely triggered avalanche by some skiers earlier in the day. They triggered it from about 60' away.