Regions
South Coast Inland.
Touchy storm slabs reactive to human triggers. Conservative decision making will be CRITICAL to playing safe in the mountains this weekend.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Saturday night: 20-25 cm new snow / Moderate to strong, southwest winds / Freezing level sea level.Sunday: 0-5 cm new snow / Moderate, southwest winds/ Freezing level sea level.Monday: Mostly cloudy with flurries / Light to moderate, southwest winds / Freezing level sea level.Tuesday: Mix of sun and cloud / Light, southwest winds/ Freezing level sea level.
Avalanche Summary
New storm slabs will likely have a poor bond to the old snow surfaces and be reactive to human triggers, especially on leeward slopes that are more wind loaded. In thin areas to the north, storm slabs could potentially step-down to deeper weak layers.
Snowpack Summary
15-25 cm of new snow has buried a wide variety of old snow surfaces including stiff wind slab or wind effected snow at upper elevations, sun crust on steep southerly slopes, surface hoar and surface facets in sheltered locations. An additional 20-25 cm of new snow is expected by Sunday morning, bringing storm totals up to 35-50 cm(lower amounts in the north). The mid-January surface hoar and facet interface is now buried 50-80 cm and the mid-December facets down 90-120 cm remain a concern especially in shallower snowpack areas like the Duffey, Hurley and/ or South Chilcotins. These deeper weaknesses warrant monitoring especially through periods of more load. In southern areas (Coquihalla), the lower snowpack is reportedly well settled(stronger), than it is to the north.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.