Conservative decision making and disciplined terrain use is the name of the game when these tricky avalanche conditions persist. Check out the new Forecaster Blog @ avalanche.ca.
Confidence
Fair - Due to the number of field observations
Weather Forecast
A weak system will slide down the coast and start to affect the Interior on Saturday bringing mostly light snowfall amounts up to 10 cm. Ridgetop winds will be light-moderate from the west, switching to a northerly flow by Sunday. Alpine temperatures will hover around -15 and drop to -20 later Sunday. Conditions will remain cold and dry through Tuesday.
Avalanche Summary
Natural avalanche activity has tapered off, however; on Thursday an explosive triggered size 2.5 slab avalanche initiated in the mid-December surface hoar and stepped down to the early November rain crust. Yikes! Definitely something to keep on your radar.
Snowpack Summary
Storm snow totals 30-70 cm above a very touchy surface hoar layer that was buried mid-December. Below 2100 m this storm slab sits on a thick, solid crust/ surface hoar combo and has been acting as the perfect sliding layer. This persistent slab remains touchy to the weight of a skier and rider, especially in wind effected areas. A hard rain crust with facets from early November is buried over 1 m down and has recently been reactive with larger loads (explosives and smaller avalanches) especially in the Northern part of the region where the snowpack is thinner.
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.