Regions
Banff Yoho Kootenay.
Pay attention to the temperatures on Wednesday. The warming trend we are experiencing will increase the avalanche hazard. The Banff area in particular is experiencing very warm temperatures.
Weather Forecast
Wednesday will be mostly cloudy with some light snowfall expected. Up to 10 cm of new snow can be expected along the divide. Freezing levels will be around 1600 m in the Lake Louise area and 1700 m in the Banff area. A slight cooling trend is forecast for Thursday.
Snowpack Summary
In general the snowpack in this area is weak and facetted. Along the divide where the snowpack may be deeper a stronger midpack can be found. Moderate to strong SW winds over the last couple of days have created scouring, wind effect and hard and soft wind slabs in the alpine.
Avalanche Summary
A Class 2.5 avalanche was observed running over Rogan's Gully ice climb on Cascade on Tuesday. This was associated with above freezing temperatures in the Banff area today. Several skier triggered avalanches have been reported over last few days. These have released on the weak facet layer in the midpack.
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.