Extra caution should be used around tree line, especially in areas that have not seen a lot of recent traffic.A Special Public Avalanche Warning is in effect for this region
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
A low pressure system will brush the southern part of the Province as it moves north eastward into Alberta Saturday afternoon and Sunday morning. The southern Purcells may receive 5 to 10cm of moist snow from this system . Freezing levels will fluctuate between 500 m overnight to 1000 min the afternoon on Sunday. Monday the freezing level will again rise to 1000 m with cloudy skies and a slight chance of flurries
Avalanche Summary
Numerous reports from yesterday of natural, skier remote, skier controlled and explosive result avalanches up to size 2.5. Most of these failed on a persistent weak layer 30 to 50 cm from the surface consisting of surface hoar or a crust/facet interface. Strong winds, new snow and rising temperatures increase likelihood of avalanches this weekend. Human triggering remains a real possibility through the forecast period.
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.