Avalanche Forecast North Columbia

Tuesday 5th February 2019

Avalanche Danger Ratings Tue 5th Feb 4:12PM Danger Ratings Alpine: Moderate Danger Ratings Treeline: Considerable Danger Ratings Below Treeline: Considerable Persistent Slabs Persistent Slabs Wind Slabs Wind Slabs

Avalanche Canada Forecaster: kdevine

Date Issued:

Valid Until:

The unusual danger rating is due to a buried weak layer that exists mainly at treeline and below. It is easily triggered by humans and there is the potential for large avalanches at lower elevations. Choose low angled terrain, especially in the trees

Confidence

High -

Weather Forecast

TUESDAY NIGHT - Clear with cloudy periods / northwest winds 10-15 km/h / alpine low temperature near -19WEDNESDAY - Mainly sunny / northwest winds 10-15 km/h / alpine high temperature near -16THURSDAY - Mainly cloudy with light flurries, 3-5 cm / southwest winds 10-20 km/h / alpine high temperature near -14FRIDAY - A mix of sun and cloud with scattered flurries / northeast winds, 15-25 km/h / alpine high temperature near -16

Avalanche Summary

Natural avalanche activity began to slow down on Sunday, but a persistent weak layer that was buried in mid January continues to be reactive to human triggers. This layer is sensitive enough for humans to trigger avalanches remotely (from a distance). Human triggered avalanches up to size 2.5 were reported on both Sunday and Monday. This layer is the most reactive at treeline and below treeline.This MIN report from Monday does a great job of illustrating the sensitivity of this weak layer.Widespread avalanche activity was reported on Friday and Saturday. Numerous natural and explosives triggered avalanches to size 3.5, and human triggered avalanches to size 2 were reported. Many of these avalanches were triggered remotely (from a distance) and failed on the mid January 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.

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

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 recent winds in many areas, forming wind slabs on all aspects due to shifting wind directions.

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

Aspects: All aspects.

Elevations: Alpine.

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