Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Regions
Jasper.
More forecast snow and strong winds will increase the avalanche danger into the weekend.Avalanche control is planned between Parkers Ridge and Sask. Crossing on Wednesday Dec. 19th. Expect intermittent closures.
Weather Forecast
Stormy weather is expected into the weekend as a series of coastal lows bring moisture over the region. The weather models don't agree but 35cm of snowfall could fall between Wednesday and Friday evening with gusting strong westerly winds. A detailed mountain weather forecast is available from Avalanche Canada.
Snowpack Summary
Up to 30 cm of new snow has been blown into fresh wind slabs by moderate SW winds. The December 11th persistent weak layer (facets, crusts and isolated surface hoar) has been buried by up to 80cm of fallen snow - this has been loaded into lee terrain by moderate to strong SW wind. The deep persistent weakness still lingers near the ground.
Avalanche Summary
A lack of visibility is hiding any new avalanches but on Tuesday a field team at Parkers Ridge observed many signs of instability (shooting cracks and whumphs) and spooky sudden result in snow pits. Last week, a natural avalanche cycle and subsequent avalanche control work resulted in many slab avalanches up to size 3.5 in the Parkers ridge area.
Confidence
Timing, track, or intensity of incoming weather system is uncertain.
Problems
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.
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.