Regions
Northwest Inland.
Sustained and shifting winds are driving a wind slab problem at higher elevations. The potential for a wind slab release to trigger a deeper persistent slab can't be overlooked.
Weather Forecast
Saturday: A mix of sun and cloud with isolated flurries and a trace of new snow. Light southwest winds. Alpine temperatures of -9. Sunday: A mix of sun and cloud with isolated flurries and a trace of new snow. Moderate to strong southwest winds. Alpine temperatures of -8. Monday: Cloudy with sunny periods. Light southeast winds. Freezing level rising to 1000 metres with alpine temperatures of -7.
Avalanche Summary
No new avalanches have been reported, but a report from the north of the region detailed a remotely triggered Size 2 storm slab releasing on a northeast aspect at 1400 metres on Wednesday. The slab depth was 50 cm. Numerous natural avalanches up to size 2.5 were reported from the west of the region in the Howsons on Tuesday. Natural avalanches up to size 2.0 were reported from the Hankin area on Monday.
Snowpack Summary
At treeline and above, ongoing winds have been redistributing recent storm snow and light new snow amounts into wind slabs in lee terrain. New snow amounts taper with elevation and lie over a supportive crust at about 1300 metres and below. At higher elevations, the recent snow is incrementally loading a weak interface that was buried in late February. The interface is composed of facets, crusts, and surface hoar and may be 40-60 cm deep. There's uncertainty about the distribution and reactivity of this interface, but it recently proved reactive under skier traffic in the north of the region. The mid-pack is well consolidated, but sits above weak, sugary snow near the ground. This deeper basal weakness remains an ongoing concern in thin rocky start zones and in shallow snowpack locations.
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.