Regions
Banff Yoho Kootenay.
An avalanche cycle is expected over the next 24 hours as a reasonably intense storm passes through the area. Large avalanches on the persistent layers would not be surprising with cornices, windslabs and even loose dry avalanches as possible triggers
Weather Forecast
A low is passing over the Jasper area early Friday afternoon with a cold front to follow into the forecast region. Heavy snowfall combined with strong SW winds in the alpine are expected to create rapid loading. Temperatures have reached their peak Friday afternoon and can be expected to cool to -10C values at Treeline for Saturday morning.
Snowpack Summary
Wind slabs are developing at tree line and above with incoming snow and strong SW winds. Below 1850m a thin rain-crust sits below 10-15cm of recent snow. Common throughout the region are the weak facets and depth hoar in the lower half of the snowpack with a 40 to 60 cm stiff slab sitting above them.
Avalanche Summary
No new avalanche activity was observed or reported on Thursday.
Confidence
Intensity of incoming weather systems is uncertain on Friday
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.