Observation Date: 02/20/2012

Route/Location:
Saturrday and Sunday – ski various slopes of all slope angles and aspects in the North Fork of Lost Horse creek

Monday – ski south face of Canyon Peak and Downing Mountain on the Sawtooth Canyon/Canyon Creek divide

Weather:
Light snow all weekend. Snow totals at ridgelines (9,000′) were in the 8″ range. Snow totals tapered to less then 3″ below 6000′. Moderate but steady south winds to approx. 25 mph above 7,000′ all weekend, calm below about 7,000′.

Wind:

New Snow:

Snow DensityThe mass of snow per unit volume, but often expressed as a percent water content. New fallen powder has a low densityThe mass of snow per unit volume, but often expressed as a percent water content. New fallen powder has a low density (3-10%), while heavy or wet snow is more dense (10-20%). (3-10%), while heavy or wet snow is more dense (10-20%).:

Avalanche Activity:
I made the following observations over the course of 3 days in the Central Bitterroot (Lost Horse and Sawtooth creeks). Storm totals were only enough to produce avalanche concern on wind loaded aspects. Avalanches were all limited to the new/weekend snow. Soft slabs ranging from 2 – 12″ in depth were easily ski triggered on all steep wind loaded aspects on Saturday and Sunday. Slabs were already healing up on Monday, but I was still seeing shooting cracks in heavily windloaded slopes on all aspects, and turned around on early on the steep windloaded South face of Canyon Peak as a result. This storm came in with a little more wind than normal. Also, the wind direction (south) was atypical.

I did not notice any recent natural avalanche activity.

I did not dig a pit all weekend, but my impression is that the Bitterroot range did not develop as much surface hoarFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dewFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dew. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried.. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried. during the early Feb. high pressure as the Rattlesnake and more northerly mountains. This impression was based on not seeing much surface hoarFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dewFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dew. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried.. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried. during tours at the end of the high pressure system in Boulder, Bass and Kootenai Creeks. Also there was a lack of cracking/collapsingWhumpf has actually been adopted as a technical avalanche term to describe the sound of a collapsing snowpack when you cross the snow. A sign of instability. as a result of the new snow. One exception is along the very tops of ridgelines, where I did get some collapsingWhumpf has actually been adopted as a technical avalanche term to describe the sound of a collapsing snowpack when you cross the snow. A sign of instability. and soft slabA relatively cohesive snowpack layer. A layer of snow stronger than underlying layers. releases which I think were caused by a very thin surface hoarFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dewFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dew. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried.. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried. layer. Another exception is surface hoarFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dewFeathery crystals that form on the snow surface during clear and calm conditions - essentially frozen dew. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried.. Forms a persistent weak layerA snowpack layer with less strength than adjacent layers. Often the layer in the snowpack where an avalanche fractures. once buried. which developed along the creek bottoms, but they haven’t received enough new snow to pose an avalanche threat.

Observed Danger Rating:

Other Comments:

Observer: Brian Story