Avalanche Forecast

Moderate -

THURSDAY NIGHT: Lingering flurries with 2-5 cm of snow, strong wind from the southwest, freezing level rapidly dropping, alpine temperatures drop below -10 C.FRIDAY: Cloudy with isolated flurries in the morning then clearing in the afternoon, moderate wind from the west, alpine temperatures around -8 C.SATURDAY: Clear in the morning then increasing cloud late in the afternoon, light wind from the southwest, alpine high temperatures around -8 C.SUNDAY: Scattered flurries with 2-4 cm of snow, light wind from the southwest, alpine high temperatures around -6 C.

Extensive 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.On Wednesday, a large (size 2.5) persistent slab avalanche was triggered in the Golden area by a skier breaking a cornice onto a northeast-facing slope. 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 in the Golden area on Saturday when a size 2.5 avalanche was remotely triggered from 50-100 m away on a northwest aspect at 2250 m.

Thursday's storm delivered 10-20 cm of new snow and strong winds promoted widespread slab formation. Approximately 50-100 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). 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.