Avalanche Forecast

Issued: Mar 7th, 2021 4:00PM

The alpine rating is moderate, the treeline rating is low, and the below treeline rating is low. Known problems include Wind Slabs.

Avalanche Canada astclair, Avalanche Canada

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Triggering wind slabs in steep, leeward terrain features may be possible at upper elevations. Monitor for these conditions where you travel. 

Summary

Confidence

Moderate - Confidence is due to a stable weather pattern with little change expected. Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

Dry conditions for the next few days

Sunday night: Clearing overnight, isolated flurries with trace accumulations, moderate southwest wind, freezing level dropping to valley bottom.

Monday: Mainly sunny, light variable wind, freezing level rising to 1500 m and dropping to valley bottom. 

Tuesday: Mix of sun and cloud, light southwest wind, freezing level rising to 1400 m and dropping to valley bottom.

Wednesday: Mix of sun and cloud, moderate west wind, freezing level rising to 1200 m and dropping to valley bottom. 

Avalanche Summary

On Saturday, operators reported ski cutting small (size 1) pockets of the recent storm snow. Observers also reported loose dry sluffs in the new snow in steep terrain. See this MIN report for an example.

During last week's warm weather, numerous small to large (size 1-2) wet loose avalanches released naturally on south-facing aspects up to 2000 m. In a shallow snowpack area east of the region near Apex, a large (size 2) slab avalanche released naturally on a weak layer of facets near the ground.

Last weekend, large explosives produced very large (size 2-3) results at Kootenay Pass. In thin snowpack areas on solar aspects, a few of these large avalanches are suspected to have stepped down to the January layer described in the snowpack summary.

Snowpack Summary

Up to 15 cm of new snow accumulated over the weekend in favored areas while periods of moderate southwest wind formed shallow wind slabs in lee features at upper elevations. The new snow fell on a variety of snow surfaces including hard wind-pressed snow, a melt-freeze crust, or settled powder in sheltered, shaded areas. Additionally, a thin layer of surface hoar may also exist at this interface that could increase the likelihood of triggering wind slabs above.

Deeper in the snowpack, a persistent weak layer from late January is buried 80-150 cm deep and is composed of a combination of surface hoar, crusts, and facets. There is some lingering uncertainty about whether this problem remains reactive on isolated upper elevation slopes on solar aspects in thin snowpack areas. 

As described in this MIN report, shallow snowpack areas in the east of the region may harbor a faceted basal snowpack. This structure can typically be managed by avoiding shallow rocky areas where the snowpack transitions from thick to thin. 

Terrain and Travel

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Extra caution for areas experiencing rapidly warming temperatures for the first time.

Problems

Wind Slabs

An icon showing Wind Slabs

Incremental snowfall and moderate winds are expected to form shallow wind slabs in lee features at upper elevations that may be possible to trigger.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Mar 8th, 2021 4:00PM