Regions
Northwest Inland.
Old wind slabs may still be reactive to human triggering.
Confidence
Moderate - Due to the number and quality of field observations
Weather Forecast
Spring like daily fluctuation in temperature. TUESDAY: isolated flurries, light southwest winds, 1200m freezing level. WEDNESDAY: partly cloudy with flurries, light west winds, 1000m freezing level. THURSDAY: mainly sunny, light southeasterly winds, 1000m freezing level.
Avalanche Summary
Avalanche activity has slowed since the weekend however cornices continue to collapse naturally. Occasionally these collapsing cornices have triggered slabs on the slopes below.
Snowpack Summary
New snow is falling on widely wind effected surfaces in the alpine and at treeline. Moist snow can be found at lower elevations and on slopes that see direct sunlight. In the north of the region a crust and/or surface hoar from early in March or late February can be found in the upper meter of the snowpack. A deeper layer of surface hoar from early January can be found in isolated locations across the region between 60 and 140 cm down. There hasn't been any avalanche activity reported on this layer for a couple of weeks now and it is becoming less of a concern. In shallower areas the snowpack sits on a weak base layer of facetted snow. This layer has been sporadically active in the north of the region, responsible for several large avalanches in unsupported alpine terrain. Cornices are large and fragile.
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.