Observation: White Pine

Observation Date
2/6/2014
Observer Name
Bruce Tremper
Region
Salt Lake » Little Cottonwood Canyon » White Pine
Location Name or Route
White Pine to end of upper cirque
Weather
Sky
Obscured
Precipitation
Light Snowfall
Wind Direction
West
Wind Speed
Moderate
Weather Comments
Cold with light snow and moderate pre-storm wind all day from the west. The visibility went in and out with light snow squalls.
Snow Characteristics
New Snow Depth
8"
New Snow Density
Low
Snow Surface Conditions
Powder
Snow Characteristics Comments

I went into White Pine to look at a couple reported human triggered avalanches from yesterday including one that reportedly caught 3 people as they were skinning up. Despite wandering all over the White Pine drainage, I did not find either one. I suspect that the strong wind filled in the evidence after they were triggered.

Extensive wind damage approaching 10,000' and higher from winds probably yesterday. Widespread, lurch-and-jerk wind slabs and hard slabs on all aspects resting on the light snow from before the wind. Down out of the wind, the surface snow remains light and powdery with a supportable base.

Red Flags
Red Flags
Recent Avalanches
Wind Loading
Cracking
Poor Snowpack Structure
Red Flags Comments
The snowpack has been fairly well behaved for the past week or so but the stiff, recent winds changed everything. There are widespread wind slabs approaching 10,000' and higher consisting of hard slabs and lots of punchy, soft slabs resting on the old low density snow surface. In the shallow snowpack areas, these wind slabs rest on faceted snow. Many of them crack but they were not very sensitive except when resting on weak, faceted snow on steep slopes. I stayed on gentle slope angles all day.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Increasing Danger
Problem #1 Comments

No lack of fresh wind slabs in above tree line alpine terrain, mostly above 10,000'. These are both hard and soft. Most sit on top of the low density new snow from before the wind so they are not cracking very much or collapsing. I didn't get on any steep slopes to test them, though. Occasionally, I could find some places where the wind slabs sat on weak, shallow, faceted snow and they were much more touchy. I suspect this was the situation for the human triggered avalanches yesterday.

Avalanche Problem #2
Problem
New Snow
Problem #2 Comments

In the shallow snowpack areas, the added load of wind deposited snow and the expected new snow over the next several days will undoubtedly overload various layers of weak, faceted snow. It's going to be almost impossible to know where the danger areas are located because the snowpack is extremely spatially variable. In general, the areas outside of the Cottonwood Canyons are weaker and the steep, thin, rocky areas as well. Plus, there are the repeater slide paths. It's just going to be a crap shoot.

Snow Profile
Aspect
North
Elevation
9,200'
Slope Angle
32°
Comments

Here is a 2 minute video of my snowpit profile at 9,000' north facing slope in White Pine.

Video

Extensive wind damage above 10,000'.

Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Considerable
Coordinates