Obs-Snow Profile: Mt. Aire 2/27/2011

Observer Name:

Bruce Tremper

Region:

Mt. Aire
Mill Creek Canyon
Salt Lake

Observation Date:

02/27/2011

Weather

Sky:

Scattered

Weather Comments:

Cloudy and foggy in the morning with clear in the afternoon.

Snow Characteristics

New Snow Depth:

12"

New Snow Density:

Medium

Snow Surface Conditions:

Powder

Snow Characteristic Comments:

Still very nice powder on the sun sheltered slopes with a bit of a sun crust forming on the sun exposed slopes.

Primary Concern

Primary Concern:

New Snow

Probability:

Moderate

Elevation:

High

Trend:

Less Dangerous

Primary Concern Comments:

It's a hard call whether the surface density inversion or to persistent slabs are the primary concern. I choose the storm snow because there is a funky density inversion within the new snow from the wind on Friday night and you can see several steep slopes that released during the storm a couple days ago about a foot deep. Several others have cracks where they collapsed.

However the instabilities within the new snow seem to have settled out quickly. It's still a little spooky because it's difficult to isolate a column but there just is not any stored elastic energy in the snow to propagate a fracture. In other words, there is a red light for strength with a green light for energy, thus you get initiation, but no propagation.

I would guess this would go away quickly because most of the instability has already healed up.

Secondary Concern

Secondary Concern:

Deep Slabs

Aspect:

North

Northeast

East

Northwest

Elevation:

High

Mid

Trend:

Less Dangerous

Secondary Concern Comments:

In the core of the Wasatch, the old, persistent weak layers seem to be healed up or dormant, but in the thinner snowpack areas, they seem worse. Mt. Aire has been notorious this season for producing some of these avalanches so I wanted to see it for myself. Sure enough, the snowpack is thinner there, about 150 cm in most places, and I found some depth hoar near the ground that did propagate a fracture in one pit but not in another. In both cases, it was stubborn and you had to hit it pretty hard.

These deep avalanches are still possible to trigger but I would think they have a low probability but with high consequence.

Elevation:

7900'

Aspect:

North

Slope Angle:

snow_profile_location:

United States

40° 42' 51.4116" N, 111° 42' 2.2176" W

Observed Danger Rating:

Moderate

Forecast Danger Rating:

Moderate

Snow Profile Location

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