Avalanche Forecast

Issued: Mar 31st, 2018 4:27PM

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

Avalanche Canada mconlan, Avalanche Canada

Storm slabs exist in the south of the region from recent snowfall. This overlies a couple touchy weak layers. Be cautious on southerly aspects when the sun is out. Conservative decision-making is recommended.

Summary

Confidence

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

Weather Forecast

SUNDAY: Early-morning snowfall then mostly sunny, accumulation 2 to 5 cm with possible localized higher amounts from convective flurries, light northeasterly winds, alpine temperature -9 C, freezing level 600 m.MONDAY: Mostly cloudy with afternoon snowfall, accumulation 1 to 3 cm, light southerly winds, alpine temperature -9 C, freezing level 600 m.TUESDAY: Mostly cloudy with early-morning snowfall, accumulation 5 to 10 cm, light southwesterly winds, alpine temperature -10 C, freezing level 500 m.

Avalanche Summary

On Friday, a natural cycle within the recent storm snow occurred, failing as storm slabs and loose dry avalanches. They were small to large (size 1 to 2), on all aspects, and at all elevations. See this MIN report to observe some of the avalanches.Previously in the 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

Thursday’s storm dumped 30 to 40 cm of snow in the south of the region, such as around Terrace and Shames.  There is now about 70 to 90 cm of storm snow that overlies two layers of surface hoar, which were buried early- and mid-March. At low elevations, the storm snow sits on a melt-freeze crust.Dormant weak layers exist deeper in the snowpack.  Layers of crusts, facets, and isolated surface hoar from mid- and late-February are buried 100 to 150 cm.  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 about 50 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.
Use extra caution in open trees and sheltered features where surface hoar may be preserved.Be aware of the potential for large, destructive avalanches due to buried surface hoar.

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

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Storm Slabs

An icon showing Storm Slabs
Recent snowfall of up to 40 cm in the south of the region have formed reactive storm slabs.  Slabs may be more reactive on sunny and lee slopes. Observe for signs of instability within the snow, such as cracking, whumpfing, and avalanche activity.
If triggered, storm slabs may step down to deeper layers, resulting in large avalanches.Approach lee and cross-loaded slopes with caution.Be aware of the potential for loose dry avalanches in steep terrain where snow hasn't formed a slab.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Valid until: Apr 1st, 2018 2:00PM

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