Avalanche Forecast

Moderate - Intensity of incoming weather systems is uncertain.

WEDNESDAY NIGHT: Cloudy with isolated flurries, accumulation up to 5cm. Light to moderate south-southwest wind. Freezing level below 1000m. THURSDAY: Snow, 10-25cm new snow, increasing through the day. Moderate southwest wind with strong to extreme gusts. Freezing level rising to 1600m. FRIDAY: Mix of sun and cloud, isolated flurries. Light west wind with strong gusts. Freezing level valley bottom. SATURDAY: Mix of sun and cloud. Light west wind. Freezing level valley bottom.

Extensive recent avalanche activity has occurred in the Purcells since December 12. Explosives and skier traffic are triggering large (size 2) avalanches, and although natural avalanche activity has started to subside, human-triggered avalanches remain a concern. Over the weekend, a small sluff triggered by a skier stepped down to a deeply buried weak layer (likely basal facets) causing a size 2 avalanche on Sunday. Another very notable avalanche occurred on Saturday when a size 2.5 avalanche was remotely triggered from 50-100m away on a northwest aspect at 2250m.

Approximately 60-90 cm of recent snow sits on a weak layer of facets (sugary snow), surface hoar (feathery crystals), and a sun crust (on south facing slopes). Strong winds have promoted widespread slab formation, particularly with the most recent new snow available for transport. Another layer of surface hoar and sun crust is now buried 80-150 cm. The potential may exist for smaller avalanches to step down to this deeper layer, resulting in very large avalanches. The most likely areas for this layer to be a problem is where the surface hoar sits on the sun crust, which is most likely on steep south facing terrain at treeline. At the base of the snowpack is a crust that formed in late October. This layer is likely only a problem on large, steep alpine features with a shallow snowpack. It would likely take a large trigger, such as a cornice fall, to produce an avalanche on this layer.