Avalanche Forecast

Issued: Apr 1st, 2018 4:13PM

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

Avalanche Canada mconlan, Avalanche Canada

Storm slabs overlie a couple weak layers, which have produced large and destructive avalanches. Observe for signs of instability within the snow before committing yourself into avalanche terrain, such as cracking, whumpfing, and avalanche activity.

Summary

Confidence

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

Weather Forecast

MONDAY: Mostly cloudy with afternoon snowfall, accumulation 1 to 3 cm, light southwesterly winds, alpine temperature -10 C, freezing level 500 m.TUESDAY: Cloudy with snowfall, accumulation 10 to 15 cm, light southwesterly winds, alpine temperature -10 C, freezing level 500 m.WEDNESDAY: Mostly cloudy with light snowfall, accumulation 1 to 3 cm, light southerly winds, alpine temperature -9 C, freezing level 600 m.

Avalanche Summary

On Saturday, a large persistent slab avalanche was reported in the north of the region, failing on the early-March weak layer described in the Snowpack Discussion.  It failed on an easterly aspect around treeline.  Otherwise, there was further evidence of the natural cycle that occurred on Friday within the recent storm snow, with storm slab and loose dry avalanches.  They were small to large (size 1 to 2), on all aspects, and at all elevations.Last week, large persistent slab avalanches were reported at all elevation bands, on east to northeast aspects.  These were failing on the early- and mid-March layers described in the Snowpack Discussion.

Snowpack Summary

Expect to find a surface crust on southerly aspects from the weekend’s clear skies.In the south of the region, there is about 70 to 90 cm of storm snow from last week that overlies two layers of surface hoar, which are most prominent on north to easterly aspects and were buried early- and mid-March. In the north of the region, these layers are around 40 cm deep.  At low elevations, last week’s storm snow sits on a melt-freeze crust.Near the bottom of the snowpack, weak and sugary facets exist in shallower parts of the region, such as the far north.

Problems

Persistent Slabs

An icon showing Persistent Slabs
A weak surface hoar layer buried 50 to 90 cm has produced large slab avalanches that have propagated widely. It is best to avoid sheltered north to easterly slopes, where this layer is most likely to be a problem.
Be aware of the potential for large, destructive avalanches due to buried surface hoar.Use extra caution in open trees and sheltered features where surface hoar may be preserved.

Aspects: North, North East, East, South East.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Storm Slabs

An icon showing Storm Slabs
Although storm slab activity has decreased, it is still possible to trigger them. Slabs may be more reactive on lee slopes where the snow has more slab properties.
Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.Approach lee and cross-loaded slopes with caution.If triggered, storm slabs may step down to deeper layers, resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Valid until: Apr 2nd, 2018 2:00PM

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