Regions
Banff Yoho Kootenay.
There is uncertainty around the deep persistent facets, how they will react to a user, and what will trigger them naturally. The best way to manage this uncertainty is through conservative terrain choices, and limiting exposure to overhead hazard. SH
Weather Forecast
A slow cooling trend over the next 3 days (-7 to -12C in the alpine) with dying SW winds. No major snow is in the forecast.
Snowpack Summary
10-30cm of new snow in the region(deeper amounts near the divide) with some wind slabs formed in lee terrain. The upper snowpack consists of wind layers of various thicknesses. The lower snowpack consists of facets and depth hoar, and below treeline the entire snowpack mainly consists of facets to ground.
Avalanche Summary
Many avalanches to size 2.5 have been reported in the last 24 hours. A size 1.5 skier accidental in the canyon on the approach to Bow Hut was reported yesterday with no involvement. A size 2 avalanche was reported from yesterday afternoon over the ice climb Cascade Falls, and explosive results at Lake Louise ski hill to size 2.5 to ground.
Confidence
Due to the number and quality of field observations on Thursday
Problems
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.
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.