Regions
Kootenay Boundary.
Daytime heating and solar radiation will play a large role in the danger rating for the next few days.
Confidence
Good - Timing or intensity of solar radiation is uncertain
Weather Forecast
Overnight: Temperatures cooling down, nil precip., freezing level at valley bottom, light to moderate SW winds.Sunday: Sunny with some cloudy periods, nil precip., variable light winds. Freezing level around 1300m.Monday: Sunny with some cloudy periods, nil precip., light winds, freezing level to 1300m.Tuesday: Sunny with some cloudy periods, nil precip., light winds, freezing levels rise to around 1700m.
Avalanche Summary
Recent explosive controls reported results in storm snow only. Sluffing in steep terrain, snowballing and pinwheel activity on steep solar aspects.
Snowpack Summary
The storm slab in the North is close to a metre thick and appears to be more touchy than in most of the rest of the region. The Rossland area appears to have a shallower snowpack and weak basal facets continue to be a concern where wind slabs and storm slabs have added load above the weak layers. The forecast very warm alpine temperatures may result in periods of rapid warming of the wind and storm slabs above weak layers. Periods of strong solar radiation may cause moist or wet loose snow avalanches and/or cornice falls which could result in large additional loads above deeply buried weak layers. Surface hoar has been reported forming on protected north slopes along with facetting of surface HST and storm slab in protected locations.
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.
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.
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.