Regions
South Coast Inland.
Human triggered avalanches remain likely on Saturday at treeline and above. Use small slopes with low consequence to test the bond of the storm snow.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Seasonal temperatures and isolated flurries through the weekend. Significant warming Monday onwards. SATURDAY: 15-20cm possible for the Coquihalla and Duffey zones by Saturday morning. Mostly cloudy with isolated flurries. / Light to moderate southwesterly winds/ Freezing level around 900 m / Alpine highs to -7 Celsius SUNDAY: Cloudy with sunny breaks / Light, southwesterly winds / Freezing level rising to 1400 m in the afternoon. MONDAY: Sunny with cloudy periods, warming significantly with highs to +1 Celsius / Moderate southwesterly winds / Freezing level around 2000 m.
Avalanche Summary
A widespread natural avalanche cycle (to Size 2.5) occurred on all aspects and elevations at treeline and above from Thursday into Friday.
Snowpack Summary
An additional 40+ cm of snow on Thursday added to the 35-50 cm (lower amounts in the north) of recent storm snow. Temperatures rose on Thursday afternoon, increasing the likelihood slab avalanches with the heavier snow on top of lighter, drier snow. All this storm snow is sitting on 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. The mid-January surface hoar and facet interface is now buried 90-120 cm and the mid-December facets down 130-160 cm still remain a concern especially in shallower snowpack areas in the Duffey, Hurley and/ or South Chilcotins. These deeper weaknesses warrant monitoring, especially through periods of rapid loading. 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.