Avalanche Forecast

Issued: Mar 6th, 2018 3:59PM

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 shorton, Avalanche Canada

Avalanches are most likely on slopes getting hit by direct sunlight, although triggering persistent slab avalanches remains a concern on all aspects.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Thursday

Weather Forecast

WEDNESDAY: Mix of sun and clouds, moderate west wind, freezing level rising to around 1400 m.THURSDAY: Flurries increasing throughout the day with 5-10 cm of snow by the afternoon, moderate southwest wind, freezing level rising to around 1400 m.FRIDAY: Another 5-10 cm of snow then clearing in the afternoon with freezing level rising to around 1400 m.

Avalanche Summary

Activity on Monday was limited to dry loose sluffing in steep terrain. On Sunday, a skier triggered a large avalanche on a north treeline slope in the Rossland area that failed on a surface hoar layer 80 cm below the surface. Skiers in the Rossland area also experience whumpfing and ski cut a size 1 wind slab on a east aspect at 1700 m. Elsewhere in the region, a natural wind slab was observed on a northwest aspect at 2150 m and explosive control produced numerous size 2 storm slabs on south aspects.The main concern on Wednesday will be persistent slabs and storm slabs becoming reactive on slopes getting hit by direct sunlight.

Snowpack Summary

Isolated flurries have delivered sporadic and localized accumulations of new snow. Snowfall amounts from the past week are 40-60 cm with the exception of the Rossland area which received 80-100 cm.A mix of interfaces 50-100 cm below the surface will potentially remain reactive to human triggering and have given sudden results in recent snowpack tests. This includes small surface hoar on polar aspects and a sun crust on solar aspects.Two deeper weak layers that formed in January and December are gradually gaining strength. Several surface hoar and facet layers are buried 1 to 2 m below the surface and there is a crust/ facet interface near the base of the snowpack. No avalanches have been reported on these layers for a few weeks and they are thought to have gone dormant at this time.

Problems

Persistent Slabs

An icon showing Persistent Slabs
A few weak layers exist 50-100 cm below the surface and include surface hoar on north-facing terrain and sun crusts on south-facing terrain.
Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Be cautious on convex rolls at and below treeline where buried surface hoar may be preserved.Choose well supported terrain without convexities.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 2.5

Storm Slabs

An icon showing Storm Slabs
Storm snow from the past week may still be reactive to human triggers, especially in areas like the Rossland area that received up to 80 cm of snow. The sun could make the storm slabs more reactive.
Approach steep lee and cross-loaded slopes with caution.Be alert to conditions that change with elevation.Minimize exposure to steep, planar, south facing slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Mar 7th, 2018 2:00PM

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