Purcells

An additional 5 to 10 cm of snow Tuesday night combined with strong to extreme wind may allow for natural avalanche failure Wednesday. Seek out conservative terrain free of overhead hazard.

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Tuesday

A series of powerful pacific frontal systems are taking aim at BC this week, the Interior Ranges are poised to receive significant snow and wind. TUESDAY NIGHT: Freezing level around valley bottom, moderate to strong southwest wind at treeline, strong to extreme southwest wind in the alpine switching to northwest/west pre-dawn, 5 to 10 cm of snow.WEDNESDAY: Scattered cloud cover in the morning clearing to a few clouds in the afternoon, freezing level near valley bottom, west/northwest wind, moderate to strong at treeline, strong to extreme in the alpine, trace of snow with convective locally heavy flurries possible. 2 to 8 cm Wednesday night.THURSDAY: Overcast, freezing level around 1500 m, moderate southwest wind at treeline, strong to extreme westerly wind in the alpine, 2 to 5 cm of snow.FRIDAY: Broken cloud cover clearing to a few clouds in the evening, freezing level beginning around 1500 m potentially rising has high as 2000 m, light southerly wind at treeline, moderate southwest wind in the alpine, trace of precipitation possible.

On Monday avalanche activity was limited to small loose dry avalanches from steep rocky terrain.  Several size 1.5 natural wind slab avalanches were reported from a steep south through southwest facing alpine feature on Friday.

As of Tuesday afternoon the storm has produced 10 to 20 cm of new snow which sits on the December 9th weak layer. This layer consists of facets, surface hoar, and a crust on solar aspects. Storm slabs are not bonding well to this interface. By Wednesday morning there could be 30 cm of storm snow on this interface out of the wind, with deeper wind slabs in lee alpine features.  There are two layers of surface hoar (weak feathery crystals) being reported in the top 15-30cm. 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.