Regions
Banff Yoho Kootenay.
Recent avalanche events are proving that it's still touchy out there (see avalanche discussion). Continue to keep your terrain choices conservative as there is a high likelihood of triggering an avalanche. SH
Weather Forecast
A few cm expected Sunday with freezing levels staying at valley bottom with light gusting strong W winds throughout the day. Winds will increase overnight into Monday as another small pulse (5cm) rolls through.
Snowpack Summary
A surface windslab 10-30 cm thick continues to be reactive in the alpine. A 50-100 cm slab overlies the January 6th weak layer of surface hoar, facets and sun crust and snowpack tests indicate an unstable bond between the two. The lower snowpack is facetted and quite weak, especially in shallower areas.
Avalanche Summary
A number of avalanche incidents with very close calls this week. The most recent was a group of 7 which triggered a size 2 Friday evening, left of the regular final approach slope to Bow Hut. It initiated at 2400m on a NE aspect, was 40-80cm deep (Jan 6th layer), and ran 350m. This fully buried 1 person, and almost fully buried another.
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.