Weather Forecast
Tonight and Sunday: A weak disturbance is forecasted to bring mainly cloudy skies, a possibility of light precipitation with light N-NE winds, freezing levels at 500 m. and alpine temperatures around -10 C.Monday: A similar situation is forecasted for early Monday but should give way to partly cloudy skies during the day with light N winds and surface freezing levels. Tuesday: A ridge of high pressure is gaining strength bringing dry and cold temperatures.
Avalanche Summary
In the Northern part of the region, small slab and loose snow avalanches were reported yesterday which would have run on the late January surface hoar either as a very thin slab or as sluffing in steep terrain. In the Southern part, an incident without any involvement was reported in which a skier would have triggered a size 1 slab avalanche in a windslab below a ridgetop on a NE facing slope.
Snowpack Summary
In the Southern part of the region, the remaining recent snow has been redistributed by moderate to strong winds from the SW-W to build new windslabs in the alpine and at top of treeline. The bond between these new slabs to the underlying surface is now expected to be good. This new snow would also be sitting on a surface hoar layer on N aspects below treeline. Below 1200 m, very icy conditions exist with thin coverage. In the Northern part of the region, 5-10 cm of light snow is sitting over various surfaces, hard windslabs in the alpine, suncrust on S aspects, surface hoar in sheltered areas and facets on N aspect at treeline. There continues to be a concern for deeply buried layers of weak facetted/depth hoar crystals, this is mostly the case on slopes with a shallow and variable snowpack in the Duffey Lake and Chilcotin areas. Indeed, snowpack tests are still giving easy and moderate results in the depth hoar layer at the bottom of the snowpack.
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.
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.