Avalanche Summary
A large natural avalanche cycle is underway and wind and storm slabs, as well as deeply buried persistent weaknesses will remain sensitive to human triggers after the storm dissipates. Three separate serious incidents that are relevant for the Sea-to-Sky region occurred on Monday afternoon in the Duffey Lake and Southern Chilcotin areas of the South Coast Inland region. All of incident sites had similar terrain characteristics with north through east facing steep treeline features. Two of the avalanches likely involved the mid-December persistent weakness, while the third was reported to have released on basal facets in a shallow snowpack area with a 50-75cm depth. All of the avalanches resulted in serious injury and at least two of them were human-triggered.
Snowpack Summary
As of Monday afternoon, most areas got 30-60cm of new snow while some immediate coastal areas received over a metre, under extreme southerly winds with freezing levels peaking at around 1800m in the afternoon. Slabs overlaying various old snow surfaces, including crusts, facets, and surface hoar, buried mid-December are primed for avalanches in many parts of the region. The surface hoar is lurking generally down 80-100cm in sheltered treeline areas and below. In exposed treeline and alpine areas, weak facets with associated crusts are now down generally around a metre, but wind-loading has resulted in highly variable slab thicknesses. A recently buried thin hard rain crust that extends into alpine elevations is also providing a poor bond to overlying deep hard wind slabs. Basal facets remain a concern in shallow snowpack areas, especially where the snowpack is overlaying summer firn on slopes that have already produced deep persistent slab avalanches and have been reloaded.