Watch for a reactive soft slab below tree-line on unsupported features today. And put on some sunscreen!
Weather Forecast
Calm and clear, with plenty of sunshine. Alpine high of -8*C, light Northerly winds, and no snow today. More of the same tomorrow, with slightly warmer alpine temps (-6*C) and light winds. A system will start to move into the area by the end of the week, bringing 20-30cm by Friday with warming temp's.
Snowpack Summary
Strong southerly winds have created a variable wind slab in lee and cross-loaded alpine and tree-line features. The Jan 17 persistent weak layer (surface hoar or suncrust) is buried 30-50cm, and is most reactive in sheltered areas below tree-line.
Avalanche Summary
Numerous natural avalanches up to sz 2.5 from steep N and S alpine features (Macdonald and Tupper) were observed in the highway corridor. A cornice failure did produce a sz 3 from Tractor Shed W. Field teams were able to ski cut soft slabs to size 1 on steep, unsupported features below tree-line (Asulkan and Bostock drainages).
Problems
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.
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.