Avalanche Forecast

Issued: Dec 19th, 2018 3:48PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Persistent Slabs and Storm Slabs.

Avalanche Canada mconlan, Avalanche Canada

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Kootenay Boundary.

Expect snowfall and strong winds on Thursday, which will load a touchy weak layer buried 50 to 100 cm deep. Treat the danger as HIGH if you find more than 20 cm accumulation. It is a good day to stick to low-angled slopes without overhead exposure.

Summary

Confidence

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

Weather Forecast

WEDNESDAY NIGHT: Partly cloudy. THURSDAY: Cloudy with snowfall, accumulation 10 to 15 cm, strong southwest winds, alpine temperature -1°c, freezing level rising to 1600m over the day. FRIDAY: Partly cloudy, moderate west winds, alpine temperature -8°c, freezing level 1000m. SATURDAY: Partly cloudy, moderate southwest winds, alpine temperature -9 °c, freezing level valley bottom.

Avalanche Summary

Large (size 2 to 3) slab avalanches were triggered naturally, by skiers, and explosives on Tuesday and Wednesday. The avalanches were generally 50 to 70 cm deep and either within the storm snow or on the weak layer described in the snowpack discussion.

Snowpack Summary

Around 50 to 100 cm of recent storm snow overlies a weak layer of feathery surface hoar, sugary facets, and variable crusts. 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.Lower in the snowpack, previous weak layers from November appear inactive. These deeper layers could possibly cause problems on north-facing slopes at high elevations where the snowpack is thin.

Problems

Persistent Slabs

An icon showing Persistent Slabs
A weak layer buried around 50 to 100 cm is the primary concern. The likelihood of triggering this layer will increase during Thursday's storm. Shallower storm slab avalanches could step down to this layer and produce larger avalanches.
Choose low angle and supported terrain and watch for clues of instability.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 3

Storm Slabs

An icon showing Storm Slabs
More storm snow on Thursday will increase the likelihood of triggering avalanches. Expect to find the deepest slabs in lee terrain features, as strong southerly winds will accompany the storm.
Stick to simple terrain and be aware of what is above you at all times.Use caution in lee areas. Recent wind loading have created wind slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Valid until: Dec 20th, 2018 2:00PM

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