Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Regions
Jasper.
Exceptional amounts of snow is falling over the Bulletin Region. Avoid all Avalanche Terrain.
Weather Forecast
An ongoing storm is bringing heavy snowfall and strong winds to our area. Up to 45cm of snow has already fallen and 25cm more snow with moderate to strong winds are still forecast through Friday. Temperatures will stay warm around -5C to -8C. A detailed mountain weather forecast is available from Avalanche Canada.
Snowpack Summary
Up to 45cm of snow has fallen along the 93N. Moderate-strong SW winds have built fresh windslabs in open terrain and storm slabs in sheltered areas. Expect natural avalanche activity with the rapid loading. The Dec. 11th layer (surface hoar and facets) persists down 60-150cm, and continues to produce avalanches in shallow snowpack areas.
Avalanche Summary
Upper avalanche start zones were obscured with falling snow but we expect widespread natural avalanche activity to be occurring. Yesterday skier triggered and several natural slabs were noted on slopes with shallower snowpack around the Columbia Icefields.
Confidence
Forecast snowfall amounts are uncertain on Friday
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
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.