Reactive surface hoar layer with many rider triggered avalanches! The storm hit with strong winds and has slabbed up the snow. Combined with mild temperatures, the slab over the surface hoar layer will be more cohesive and propagation will increase.
Weather Forecast
Unsettled weather will persist into Tuesday with light snow and cloud. Temperatures are on a cooling trend and winds will be tapering down as a ridge of high pressure builds over the southern half of the Province into Wednesday.
Snowpack Summary
Close to 20cm of new snow overnight bringing recent storm snow to 45cm overtop the widespread Jan 15 surface hoar layer and crust on solar aspects. Expecting wind effected snow at higher elevations. The Dec 17 surface hoar layer is down 90-130cm overlying a crust below 2100m. The Nov 9 crust is a basal layer at the bottom of the snowpack.
Avalanche Summary
Backcountry users and field teams reporting several remote and rider triggered avalanches to size 1.5 down 20-50cm running on the Jan 15 surface hoar layer. Cheops North 4,natural avalanche dusted two riders on the uptrack. Natural avalanche cycle up to size 3.0 within the highway corridor began yesterday afternoon and into early this morning.
Confidence
Due to the number of field observations
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.