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Avalanche Forecast

Archived

Dec 21st, 2018–Dec 22nd, 2018

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

Regions

Kootenay Boundary.

A weak layer exists in our snowpack at a depth where humans can still trigger it. It is a good time to remain conservative with your terrain selection.

Confidence

High.

Weather Forecast

FRIDAY NIGHT: Clear, freezing level below valley bottom. SATURDAY: Sunny with a few clouds, moderate southwest winds, alpine temperature -9°c, freezing level below valley bottom. SUNDAY: Cloudy with light snowfall, accumulation 5cm, moderate southwest winds, alpine temperature -6°c, freezing level below valley bottom. MONDAY: Partly cloudy, light southwest winds, alpine temperature -7°c, freezing level below valley bottom.

Avalanche Summary

Large (size 2 to 3) slab avalanches were triggered naturally, by skiers, and explosives on Tuesday through Thursday. The avalanches were generally 50 to 100cm deep and either within the storm snow or on the weak layer described in the snowpack discussion. Storm slabs have stepped down to the deeper weak layer.

Snowpack Summary

Strong winds from first the south and then the northwest have redistributed the recent storm snow, producing wind slabs in lee terrain features at all elevations. Beneath this, around 50 to 100 cm of snow is poorly bonded to a rain crust and a weak layer of feathery surface hoar and sugary facets. Avalanche activity, remote triggering, and snowpack test results tell us that it is a critical layer. It is best to travel extremely cautiously with this layer in the snowpack. The lower snowpack is well-settled.

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.