Regions
Banff Yoho Kootenay.
Not much change except a break from the arctic shackles! The lack of natural activity doesn't change the fact that the lower half of the snowpack is rotten. Choose conservative terrain, especially where a wind slab sits over these facet layers. SH
Weather Forecast
Finally some respite from the "old school" winter temperatures. The morning low will still be in the "teens" but highs in the -6C range can be expected tomorrow afternoon. Alpine winds will be W to NW in the light to moderate range. On Sunday and Monday the temperatures are warmer still with strong winds from the SW.
Snowpack Summary
Lots of hard wind slabs at treeline and above from a variety of wind directions over the past while, most notably N winds from the arctic air. This has produced a reverse loading pattern in many locations. These hard slabs in many starting zone areas overly a weak, faceted snowpack with numerous instabilities in the lower half of the snowpack.
Avalanche Summary
A few natural size 2 avalanches were reported on Thursday in the Sunshine and Banff regions. These were likely cornice triggered wind slabs. No avalanches were reported 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.