Avalanche Forecast

Low - Due to the number of field observations

Late Wednesday into Thursday, the next storm will bring a bit of snow and a whole heap of wind to the Purcells. Another system is to come on Friday night. Each storm will bring a slightly warmer air mass driving the freezing level up the mountainside.WEDNESDAY NIGHT: Freezing level at valley bottom, light southwest wind at treeline, potentially strong southwest wind at ridgetop, 1 to 3 cm of snow.THURSDAY: Scattered cloud cover, freezing level around valley bottom rising to 1000 m, light southwest wind at treeline, strong southwest wind at ridgetop, 2 to 8 cm of snow.FRIDAY: Scattered cloud cover, clear skies in the evening, freezing level beginning around 1500 m potentially rising has high as 2200 m, moderate southwest wind at treeline, strong southwest wind in the alpine, trace of precipitation. 1 to 5 cm of snow/rain at lower elevations on Friday night.SATURDAY: Broken cloud cover giving way to clear skies in the evening, freezing level holding around 1500 m, strong southwest wind initially, slowing to light wind near sundown, trace of precipitation.

On Wednesday control work produced storm slab avalanches to size 2 on a variety of aspects. A size 2 avalanche on a northeast facing feature at 2200 m was sensitive to remote (from a distance) triggering. A size 1.5 natural avalanche was also reported from an east facing feature near ridgecrest. In the neighboring Glacier National Park region natural avalanches to size 3 were reported.On Tuesday loose dry avalanches to size 1.5 were sensitive to human triggering on all aspects.

The region picked up 15 to 40 cm of new snow with moderate to strong southwest wind Tuesday into Wednesday. This new snow rests on a buried weak layer (December 10th) that consists of facets, surface hoar, and a crust on solar aspects. Results on this interface are quite variable. It's very touchy in some places and less reactive in others.There are two layers of surface hoar (weak feathery crystals) 30 to 70 cm below the surface. The surface hoar is most prominent at treeline, but it may be found in sheltered alpine areas. Both of these layers may be associated with a sun crust on south aspects in some areas.Another major feature in the snowpack is a combination of a crust and faceted (sugary) snow found at or near the base of the snowpack. This layer is most prominent in the alpine.The early season snowpack is highly variable in the Purcells. Total snowpack depths vary greatly throughout the region with anywhere between 70 and 150 cm in the alpine tapering rapidly at treeline and below. In shallow snowpack areas, the bottom half of the snowpack is reportedly weak and "hollow" feeling on shady aspects due to sugary, faceted snow.