Regions
Banff Yoho Kootenay.
An avalanche cycle is occurring right now as 30-40cm of storm snow and strong winds have overloaded the weak snowpack. The winds are raking the mountains, and widespread avalanche activity was observed today. The cycle continues through Monday.
Weather Forecast
The storm pattern will continue with a slight break Saturday night and Sunday morning. The models are showing another 10-15 cm of snow by Monday, combined with very strong winds from the west. Temperatures will remain cool, with Sunday's high being -11.
Snowpack Summary
20-40 of storm snow has fallen across the forecast region over the last 36-hours, combined with a warming trend and strong to extreme winds from the SW. Widespread windslabs exist in all open areas, overlying a weak and facetted snowpack Expect leeward areas to have upwards of 100cm of drifted windslabs.
Avalanche Summary
Widespread avalanche activity today up to size 3 including both Bourgeau Left and Right waterfalls over the climbs, Healy Creek, Cascade Mountain, Corral Creek and Eagle Basin. This avalanche activity is forecast to continue on Sunday.
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.