Avalanche Forecast

Issued: Feb 13th, 2020 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 ahanna, Avalanche Canada

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Watch for wind slabs in lee features like ridge crests and steep roll-overs at alpine and treeline elevations. Fresh wind slabs may be sensitive to human triggering.

Summary

Confidence

High -

Weather Forecast

Thursday night: Up to 10 cm new snow. Winds moderate southwest. Freezing level 800 m.

Friday: Up to 5 cm new snow. Winds moderate northwest. Freezing level 1000 m.

Saturday: 5-10 cm new snow. Winds moderate southwest. Freezing level 1000 m.

Sunday: Flurries. Winds moderate northwest. Freezing level 800 m.

Avalanche Summary

A few natural loose wet size 1 avalanches were observed on steep solar aspects Wednesday. Natural wind slab avalanches up to size 2 were observed on steep, north to east facing alpine terrain on Tuesday. A few skier triggered avalanches; wind slab size 1 and a cornice size 2 were reported on Monday and Tuesday. Most were triggered on north to east aspects in the alpine, but one slid on the rain crust on a south aspect at treeline.

A very large (size 3.5) avalanche was observed on Sunday near Whistler on a steep north face at 2400 m. It is suspected to have failed on a layer of facets on a crust from late November. This very large event demonstrates the ongoing need for caution in aggressive alpine terrain.

Snowpack Summary

A bit of new snow and wind will further wind slab development in lee features at alpine and upper treeline elevations. Recent winds have varied in direction so wind slabs can be found on a variety of aspects. A rain crust sits 30-50 cm below the surface at elevations below 2000 m. The bond at this interface appears to be reasonably strong.

While weak faceted grains and crusts near the base of the snowpack have mostly not been a problem recently, a very large avalanche was observed on this layer on Feb 9. The problem appears isolated to very aggressive alpine terrain and is likely more prevalent in inland parts of the region.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Wind Slabs

An icon showing Wind Slabs

A continuing supply of light snowfall will sustain wind slab development. Recent wind direction has varied from northwest to southwest, creating wind slabs on a variety of aspects in exposed alpine and treeline terrain. Where wind slabs sit over a crust, they may be more sensitive to triggering.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 14th, 2020 5:00PM

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