Avalanche Forecast North Columbia

Wednesday 6th February 2019

Avalanche Danger Ratings Wed 6th Feb 4:46PM Danger Ratings Alpine: Moderate Danger Ratings Treeline: Considerable Danger Ratings Below Treeline: Considerable Persistent Slabs Persistent Slabs Wind Slabs Wind Slabs

Avalanche Canada Forecaster: mbender

Date Issued:

Valid Until:

There is a potential for triggering large avalanches at lower elevations due to the presence of a buried weak layer that exists mainly at treeline and below.

Confidence

High - The weather pattern is stable

Weather Forecast

THURSDAY - Mainly cloudy with light flurries, accumulation 5 cm / light southwest winds / alpine high temperature near -15FRIDAY - A mix of sun and cloud / moderate northeast wind / alpine high temperature near -17SATURDAY - A mix of sun and cloud / moderate northeast wind / alpine high temperature near -20

Avalanche Summary

A persistent weak layer that was buried in mid January continues to be reactive to human triggers. This layer is sensitive enough for avalanches to be triggered remotely (from a distance). Skier and snowmobile triggered avalanches up to size 2.5 were reported on both Sunday, Monday and Tuesday. This layer is the most reactive at treeline and below. This MIN report from Monday does a great job of illustrating the sensitivity of this weak layer.Human triggered avalanches failing on the mid January persistent weak layer have been reported almost daily for the past two weeks in the North Columbia region.

Snowpack Summary

30-80 cm of recent new snow sits on surface hoar (feathery crystals), facets (sugary snow), wind slabs and a crust on sun-exposed slopes. In many areas, recent winds have redistributed the new snow, forming wind slabs on all aspects due to shifting wind directions.The most notable feature in the snowpack at this time is a persistent weak layer that was buried in mid January, which is now buried 50-100 cm. This layer consists primarily of surface hoar, however there is also a crust associated with it on sun-exposed slopes. This layer is the most prominent at treeline and below, and continues to be produce avalanches.

Persistent Slabs Persistent Slabs

Likelihood

Likely - Possible

Expected Size

1.5 - 3

50-100 cm of snow is now sitting on a persistent weak layer of surface hoar and crust that was buried in mid January. This region has been the "hot spot" of activity on this layer, with more reactivity reported here than in neighboring regions.

Choose low angled terrain.Any steep opening in the trees should be treated as suspect right now.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

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Wind Slabs Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

30-80 cm of recent snow has been redistributed by north and east winds over the past couple of days.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered, wind slabs may step down to deeper layers and result in even larger avalanches.

Aspects: South East, South, South West, West.

Elevations: Alpine.

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