Avalanche Forecast

Moderate - Uncertainty is due to the track & intensity of the incoming weather system. Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Thursday night: Mostly cloudy with clear periods. Isolated flurries bringing a trace of new snow. Moderate wind from the south. Alpine temperatures around -21 C.

Friday: Mix of sun and cloud. Light south to southwest winds. Alpine temperatures around -18 C.

Saturday: Mostly cloudy with scattered flurries bringing 5-10 cm of new snow to most areas. Strong south to southeast winds, approaching extreme at ridgetop. Alpine high around -16 C.

Sunday: Mostly cloudy with scattered flurries bringing 10-15 cm of new snow to most areas. Moderate to strong south to southwest winds. Alpine high around -11 C.

On Tuesday and Wednesday, avalanche activity was limited to size 1-1.5 windslabs, both natural and explosive triggered. A widespread natural windslab cycle around size 2 -3 was observed Sunday through Monday morning amid reverse loading by the onset of strong outflow winds. Cornice and serac failures have also observed recently, as they typically become brittle in the cold.

Reports of deep persistent slab avalanches have been trickling in over the past week. They are associated with a November crust layer near the base of the snowpack, producing very large avalanches with crown depths of around 2 m. Observations are typically in alpine terrain, on lee or cross-loaded slopes. In one case, the slab was triggered remotely by a vehicle from shallow, rocky terrain, propagating to deeper areas. Among the earliest reports was this MIN from the storm last week.

Extensive wind effect observed at all elevations. North to east aspects in the alpine have been wind scoured, with isolated hard windslab in lees, and notable cornice growth. This wind affected surface snow may overly a layer of surface hoar in many areas, particularly at treeline. In sheltered areas, unconsolidated snow may be found well preserved by the cold temperatures.

A deep crust from mid November lurks at the base of the snowpack. A couple of recent large avalanches have run on this layer high in the alpine. 

• Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
• An atypical weather pattern has created unusual avalanche problems in this area.
• Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
• Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.