Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Wednesday: A few flurries. Light winds. Freezing level at valley bottom at night and around 1000m in the afternoon.Thursday: Light to moderate snow. Gusty winds. Freezing level is uncertain, but could rise to around 1600m.Friday: A mix of sun and cloud. Freezing level is uncertain, but could rise to around 1700m in the afternoon.
Avalanche Summary
On Tuesday, wind slabs in the size 1-1.5 range were triggered naturally and by skiers at treeline and above on slopes loaded by south-westerly winds. On Sunday, a size 1.5 avalanche released naturally on a north aspect. On Saturday, a recent avalanche was observed on a north aspect in the southern Elk Valley, suspected to have started as a wind slab and ending in moist snow. Evidence of a previous natural cycle was also reported. On Friday, explosives produced size 1-2 avalanches.
Snowpack Summary
Unsettled weather has brought snow and wind through most of the week, creating variable wind slabs and storm slabs. Newly formed 10-20cm thick wind slabs were easy to trigger on Tuesday at treeline and above. A melt-freeze crust buried below recent storm snow exists to 1900m on south aspects and 1700m elsewhere. An older rain crust is buried about 1m down. Two surface hoar layers, buried in February and now 1-2m deep, continue to exhibit sudden planar results, which have been repeated in a number of locations. This means these layers still have the potential to produce widely-propagating, destructive avalanches if triggered. Most likely triggering mechanisms are a person traveling on a thin snowpack area, or a storm slab, wind slab or cornice stepping down. Basal facets may still exist, particularly in shallow snowpack areas with steep, rocky start zones. Cornices have grown large and threaten slopes below.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.