Regions
Banff Yoho Kootenay.
We are back to a "Classic Rockies" mid winter snowpack with a weak structure that does not inspire confidence and will linger for some time. Low likelihood, high consequence periods like this are best managed with conservative decision making.
Weather Forecast
Flurries Tues night and into Weds will produce small amounts of snow on the ground (~5cm). Wind will remain light to moderate from the west. Freezing levels will remain below surface.
Snowpack Summary
Treeline height of snowpack values range from 100 to 170cm. The Feb 11 layer of sun crust and isolated surface hoar is down 20 to 50cm. The Jan 6 layer of faceted crystals is the dominant snowpack feature and is down about 50-70cm. This layer is producing whumpfing, cracking and has been responsible for much of the recent avalanche activity.
Avalanche Summary
No new avalanches to report.
Confidence
Due to the number of field observations on Tuesday
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.