A Special Public Avalanche Warning is in effect for this region.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
A last pulse of 5-10 cm snow with easing SW winds and a 1000 m freezing level is expected on Saturday ahead of a cooling and drying trend starting Sunday morning. Cloudy skies, light winds, cool temperatures and a few flurries may give way to sunny skies on Sunday/Monday. For more details check out https://avalanche.ca/weather.
Avalanche Summary
Several size 1-2 wind slabs and storm slabs have been triggered naturally and by skiers and explosives this week. Some of these failed on a persistent weak layer of surface hoar or a crust/facet interface. Winds, new snow and rising temperatures increased the size and likelihood of avalanches on Friday. Human triggering remains a real possibility through the weekend.
Snowpack Summary
Conditions are variable across the Purcells. Wind slabs and storm slabs have developed at treeline and alpine elevations. In some areas, these overlie a surface hoar or crust/facet interface from early January and may be extra touchy. This persistent weak layer is around 30-60 cm down and may be just reaching tipping point in parts of the region. A more deeply buried layer of surface hoar from December is now considered dormant. In general, the mid and lower snowpack are well settled and strong.
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.