Avalanche Forecast

Issued: Mar 8th, 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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Lingering wind slabs are the primary concern. Watch for denser, deeper drifts near ridge-crests and rollovers at upper elevations. 

Summary

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Dry conditions and diurnal cycles for the next few days

Monday night: Mostly clear, light northeast wind, freezing level 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: Mostly cloudy, isolated flurries with trace accumulations light southwest wind, freezing level rising to 1500 m and dropping to valley bottom. 

Thursday: Partly cloudy, light west winds, freezing level rising to 1500 m and dropping to valley bottom.

Avalanche Summary

On Saturday, operators reported ski cutting small (size 1) pockets in 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, a large (size 2) slab avalanche released naturally on a weak layer of facets near the ground in a shallow snowpack area east of the region near Apex, .

The most recent avalanche observed on the late January persistent weak layer was reported February 28th, when large explosives produced very large (size 2-3) results at Kootenay Pass.

Snowpack Summary

Up to 20 cm of new snow accumulated over the weekend in favored areas (Big White and Kootenay Pass). Periods of moderate winds from the southwest have likely 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 from the southwest have formed 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 9th, 2021 4:00PM

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