Wind slabs are the main concern on Tuesday as the wind continues to redistribute recent new snow onto protected slopes. Above freezing temperatures at upper elevations on Wednesday are expected to keep the avalanche danger elevated.
30-70 cm of snow fell late last week with the highest amounts in the south. Strong southwest winds have built deep wind slabs at treeline and alpine elevations on lee and crossloaded slopes.
There is currently 90-120 cm of snow sitting on top of weak a layer of sugary facets that developed above a firm crust which formed in early November. Warm temperatures at upper elevations late Tuesday and through Wednesday may increase the likelihood triggering deep persistent slabs.
MONDAY Night: Clear periods / Moderate west wind / Alpine temperature around -6 C.
TUESDAY: Mix of sun and cloud / Moderate south wind / Alpine temperature around -3 C / Freezing level rising to 1500 m in the afternoon.
WEDNESDAY: Mainly sunny / Moderate south wind / Alpine temperature around 3 C / Freezing level 2500 m.
THURSDAY: Mainly sunny with cloudy periods / Light southwest wind / Alpine temperature around -4 C / Freezing level 500 m.
There has been a report of an avalanche fatality near Pine Pass on Saturday. Reports indicate a size 3 deep persistent slab avalanche at approximately 1600 m elevation on a northeast aspect. The avalanche was approximately 55 cm deep, 800 m wide and ran 400 m in length. The avalanche was possibly remotely (triggered from a distance) and may have run on a weak layer of faceted crystals sitting on a crust that was buried in early November.
Snow depths are approximately 150 cm in the north west of the region (Pine Pass), 180 cm in the south (Renshaw, Kakwa) and 100 cm in the the north east (Tumbler ridge).
In the deeper areas, successive storms have resulted in deep powder in the upper snowpack. The wind is changing that because it will certainly be blown into denser wind deposits. The question is whether windward slopes will become stripped of the recent snow.
Most likely the most significant instabilities are within or at the base of the most recent storm snow, approximately 50-70 cm below the snow surface.
A crust forming in early November is near the base of the snowpack. In some areas facets have been reported sitting on this crust. This layer is of most concern on steep terrain in thinner snowpack areas.
