Regions
Northwest Inland.
A recent deep slab avalanche near Kispiox is a good reminder that this is a low snow year and there are lingering weaknesses at the base of the snowpack.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
WEDNESDAY: flurries, moderate southerly winds, 1000m freezing level. THURSDAY: flurries, light to moderate westerly winds, 800m freezing level 1000m. FRIDAY: flurries, moderate southerly winds, 1200m freezing level.
Avalanche Summary
A very large avalanche was triggered remotely by a skier on Monday north of the Kispiox. It released on basal facets in a steep unsupported wind loaded feature.
Snowpack Summary
Recent moderate winds have created fresh pockets of wind slab in both traditional and reverse loaded lee features in the alpine and at treeline. A couple of crusts buried in early and late February can be found in the upper meter of the snowpack. Below this a layer of surface hoar from early January can be found in isolated locations between 60 and 140cm down. We havent heard of any activity on this layer for a couple of weeks now and it is becoming less of a concern. The snowpack in shallower areas sits on a weak base layer of facetted snow. This has active layer recently, responsible for several large avalanches in unsupported alpine features over the last couple of weeks.
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.