Regions
Banff Yoho Kootenay.
A classic, weak Rockies snowpack exists and doesn't inspire much confidence. Enjoy the beautiful weather and let's hope for a little new snow to refresh the ski quality for Friday.
Weather Forecast
A weak system will bring light snow starting Thurs PM. We should see 5-10 cm's by Friday night with a clearing trend for Saturday. With this system, we will also see strong alpine winds from the west. Temperatures will cool over the period but remain -5/-10 range at valley bottom.
Snowpack Summary
Wind slabs are present in many open areas above tree line. Below this, the snow pack is quite weak and facetted in most places. The Dec 18 crust/facet/surface hoar is facetting out but still a concern in deeper snowpack areas. The bottom half of the snow pack consists of facets and depth hoar with the early november crust facetting out.
Avalanche Summary
No new avalanche activity observed on a field trip to the Helen Shoulder area
Confidence
Intensity of incoming weather systems is uncertain on Thursday
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
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.