Avalanche Forecast

Issued: Mar 30th, 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.

mconlan, Avalanche Canada

Northwest Coastal.

Up to 40 cm of snow fell in the south of the region. This snow formed storm slabs and is loading buried weak layers. Be cautious on southerly aspects when the sun is out. Conservative decision-making is recommended, as large avalanches are likely.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

SATURDAY: Sunny with afternoon clouds, light southwesterly winds, alpine temperature -6 C, freezing level 700 m.SUNDAY: Early-morning snowfall then partly cloudy, accumulation 5 to 10 cm, light northeasterly winds, alpine temperature -6 C, freezing level 700 m.MONDAY: Partly cloudy with afternoon snowfall, light southerly winds, alpine temperature -6, freezing level 600 m.

Avalanche Summary

On Thursday, large (size 2.5 to 3) storm and wind slabs were triggered naturally and by explosives, with slab depths up to 100 cm.On Tuesday and Wednesday, large (size 2 to 3) persistent slab avalanches and storm slab avalanches were reported in the region at alpine and treeline elevations, being remotely triggered (from a distance) as well as by explosives, 50 to 150 cm deep, and on northeasterly aspects.

Snowpack Summary

Thursday's storm dumped 30 to 40 cm of snow in the south of the region, such as around Terrace and Shames. This overlies last weekends storm snow, which was redistributed with strong westerly winds in exposed areas at higher elevations.Two layers of surface hoar exist in the region at depths of about 60 to 80 cm, being 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

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.

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

Likely

Expected Size

2 - 3

Storm Slabs

Up to 40 cm of snow fell in the south of the region on Thursday. Observe for signs of slab properties and instability within this snow, such as cracking, whumpfing, and avalanche activity.

Be aware of the potential for loose dry 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: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 31st, 2018 2:00PM