Regions
Banff Yoho Kootenay.
We are in a classic Rockies snowpack. Thin and rocky with a basal weakness. Forecasters have low confidence in any steeper terrain above tree line. Keep this in mind when choosing terrain to ride!
Weather Forecast
Cool temperatures, light winds and minimal precipitation are the short term forecast. Cloud cover will increase Thursday/ Friday and we might get a few snowflakes. A mild inversion is making alpine temperatures more comfortable, but doing little to destabilize the snowpack.
Snowpack Summary
In the alpine a few cm`s of new snow overlies a firm base of old wind slabs. At treeline and above, mild temperatures have helped strengthen the upper snowpack but the basal rain crust/facets remain weak. Below treeline a rain crust is present and the snowpack is solidly frozen in most areas.
Avalanche Summary
There were many ski tracks going into more aggressive alpine terrain in the Bow Summit area today. A large size 2.5 natural avalanche was also noticed on a NW aspect of Observation subpeak. This looked to be recent within the last 48 hours and is indicative of the low probability/ high consequence conditions we are currently dealing with.
Confidence
Due to the number of field observations
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.