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Avalanche Forecast

Archived

Dec 26th, 2015–Dec 29th, 2015

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

Regions

Waterton Lakes.

Mid winter conditions make for great skiing in many locations, but also makes for an increasingly complex snowpack. Evaluate the conditions carefully before committing to big terrain.

Weather Forecast

A ridge of high pressure will remain over the area until Sunday evening, a gradual rise in temperatures will be accompanied by moderate - strong Westerly winds. On Monday this ridge breaks down and a SW flow brings snow, with accumulations of up to 5cm. Tuesday the flow switches to NE, temperatures drop, and we may see a further 5cm of snow.

Snowpack Summary

Up to 55cm of low density snow has fallen since Dec 20 and is now being redistributed into wind slabs by gusty Moderate W winds. This overlies variable layers of old windslab with the Dec 9th crust below(down 50-90cm), which remains a concern as a potential weak interface, especially with cold temps promoting facetting of the snow above and below.

Avalanche Summary

Several size 1 loose snow avalanches were observed yesterday, likely triggered by the snowfall on Christmas eve.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

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.

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.

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.