Regions
Northwest Inland.
The CONSIDERABLE danger rating mostly reflects mountainous terrain to the West which received greater snowfall amounts and stronger winds. Backcountry areas to the East and South consider the Alpine rating to be MODERATE.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Saturday: Mostly cloudy with some sunny periods. Light winds from the SE, alpine temperatures -13 and freezing levels valley bottom.Sunday: Mostly cloudy with light winds from the SE. Alpine temperatures near-12Monday: A mix of sun and cloud with isolated flurries and light winds from the South. Alpine temperatures near -16.
Avalanche Summary
On Thursday, several natural wind slab avalanches were observed in the western part of the region on N-NW aspects in the alpine. Extensive sluffing and soft slabs were easily triggered by the weight of a skier, especially at lower elevations where the new snow sits on a firm crust. Reports from the Onion snowmobile area (Babine Mountains) indicated no recent avalanche activity. I suspect there will be little change with avalanche conditions over the weekend, however; isolated wind slabs may still be found in alpine locations on leeward slopes behind terrain features.
Snowpack Summary
Recent low density storm snow up to 25 cm has fallen with surprisingly little wind effect. The new snow has buried a variety of old snow surfaces including stiff wind slabs, facets, crusts and surface hoar. The new snow may have a poor bond to these interfaces, especially in places where the slab is stiffer and more cohesive due to winds. At treeline elevations the average snowpack depths are 120-190 cm and a well consolidated mid-pack of approximately up to 100 cm sits above weak basal facets (sugary snow) near the ground. Recent snowpack testing has shown sudden easy results down 25 cm on a surface hoar layer and sudden hard results down 100 cm within the facetted snow. The deeper basal weakness remain a concern, especially from thin rocky start zones and shallower 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.