Regions
Northwest Inland.
ALPINE avalanche danger is CONSIDERABLE in the North of the region where the Deep Persistent Slab problem is a more active concern.
Confidence
Moderate - Due to the number and quality of field observations
Weather Forecast
THURSDAY: flurries, light to moderate westerly winds, 1000m freezing level. FRIDAY: light snow with up to 10cm possible in the south west of Simthers, moderate southerly winds, 1200m freezing level. SATURDAY: flurries, light to moderate southerly winds, 1200m freezing level.
Avalanche Summary
A small natural avalanche cycle was reported in the northwest of the region on Tuesday. Several natural wind slab avalanches north of Bell 2 stepped down to the basal facets. A very large avalanche was triggered remotely by a skier on Monday near the Kispiox, it also released on basal facets in a steep unsupported wind loaded feature.
Snowpack Summary
Recent moderate easterly winds have created fresh pockets of wind slab in reverse loaded alpine and treeline lee features. 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. There hasn't been any activity reported 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 been an 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.