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Avalanche Forecast

Archived

Dec 19th, 2021–Dec 20th, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Glacier.

Excellent snow quality throughout the region!

Uncertainty surrounds the Dec 1 persistent weak layer and when / if it will become reactive. Assess the snowpack before committing to larger avalanche terrain.

Weather Forecast

Mainly sunny skies with cloudy periods for Monday as an Arctic High brings cold temps and 20-30km/hr Westerly winds. Tuesday will also be mainly sunny but will have isolated flurries with small accumulations of snow. More snow, 10-15cm, in the forecast for Wednesday.

Snowpack Summary

Excellent snow quality can be found throughout the Park with 40cm of new snow from the recent storm. The Dec 1 crust is ~10cm thick, buried a ranging depth of 50-100cm, and can be found up to 2300m. Facets observed above and below this crust, particularly in shallow snowpack areas at and just below tree line.

Avalanche Summary

A widespread natural avalanche cycle, up to size 3.0, occurred Saturday night as the tail end of the storm brought strong winds. The main issue for the day was managing the dry loose avalanches, which were sluffing fast.

Snowpack tests continue to give sporadic sudden results on the Dec 1 crust, particularly in shallower snowpack areas at tree line.

Confidence

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.