Avalanche Forecast

Friday Night: Flurries, accumulation 5-10 cm. Alpine temperature -4 C. Moderate to strong west wind. Freezing level 1300 m.

Saturday: Flurries, accumulation 5-10 cm. Alpine temperature -4 C. Moderate southwest wind. Freezing level 1300 m.

Sunday: Flurries. Alpine temperature -10 C. Moderate southwest wind.

Monday: Mainly cloudy. Alpine temperature -11. Moderate west wind.

Reports of avalanche activity on Thursday show several natural and explosives triggered storm slab avalanches running at tree line and in the alpine on all aspects. There were also a few human triggered storm slab avalanches to size 1.5.

That being said, explosive control work and other large triggers have consistently produced large deep persistent slab avalanches to size 3 and larger on all aspects in alpine terrain. Common characteristics of recent avalanches in the region include wide propagation, remote triggers and full depth avalanches scouring away the snowpack to ground.

15-45 cm of new snow has buried a widespread layer of surface hoar as well as a sun crust on steep south aspects. There are an additional couple of weak surface hoar layers 70-180 cm below the surface. These layers are expected to be progressively gaining strength.

The base of the snowpack in the Purcells is very weak, much weaker than in an average season. This weakness is widespread across all aspects and elevation bands. The basal layer consists of crust, facets and depth hoar.

Recent snowfalls in the past two weeks have overloaded these deeply buried weak layers resulting in numerous very large and destructive avalanches.

• Storm slabs in motion may step down to deeper layers resulting in large avalanches.
• Be aware of the potential for large avalanches due to the presence of a deep persistent slab.
• Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
• Remote triggering is a concern, watch out for adjacent and overhead slopes.