Regions
Northwest Inland.
Wind slabs have emerged as the primary avalanche problem in the region, but they aren't the only one. Our deep persistent slab problem lingers on.
Weather Forecast
Friday: Mainly cloudy with scattered flurries and a trace to 5 cm of new snow. Strong southeast winds. Alpine temperatures of -7. Saturday: A mix of sun and cloud with isolated flurries and a trace of new snow. Light to moderate west winds. Alpine temperatures of -8. Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Moderate to strong west winds. Alpine temperatures of -9.
Avalanche Summary
A report from the north of the region details 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
As our recent snow has formed a bond to the surface, ongoing winds and light new snow amounts have seen wind slabs emerge as the primary avalanche problem in the region. At lower elevations, below zero temperatures on Wednesday night likely led to a surface crust forming over previously reported moist or wet snow. At higher elevations where new snow has been accumulating, a weak interface that was buried in late February may finally have enough snow above it to form a reactive slab. 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. 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.