Avalanche Canada ccampbell, Avalanche Canada

Sea to Sky Avalanche Forecast

Jan 5th, 2012 9:16AM

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

Summary

Confidence

Good - -1

Weather Forecast

Friday: Dry with increasing cloud cover and flurries possible in the evening. Freezing levels around 700m and light winds. Saturday: Cloudy but dry with moderate precipitation starting in the evening. Freezing levels are expected to rise to 1500m and southwesterly winds increase to moderate with the onset of precipitation. Sunday: Moderate snowfall with strong southwesterly winds.

Avalanche Summary

Widespread natural avalanche activity up to Size 3 was reported on Wednesday. Fresh storm and wind slabs, as well as deeply buried persistent slabs remain sensitive to human triggers.

Snowpack Summary

Weaknesses within and under the 60-100+cm of storm snow will need some time to settle and strengthen. Persistent weaknesses remain a concern in the many parts of the region. Buried surface hoar on sheltered treeline slopes and below and facets with associated crusts in exposed treeline and alpine areas are probably down well over a metre in most places. Basal facets remain a concern in shallow snowpack areas, especially where the snowpack is overlaying summer firn on slopes that have already produced deep persistent slab avalanches and have been reloaded. Wind-loading has resulted in highly variable slab thicknesses with the potential for fractures triggered in highly sensitive thin slab areas to propagate into highly destructive deep slab avalanches. Furthermore, weaknesses within the slab create the potential for step-down fractures. A recently buried thin hard rain crust that extends into alpine elevations is also providing a poor bond to overlying deep hard wind slabs.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible

Expected Size

2 - 5
Watch for sensitive wind slabs lurking below ridgecrests, behind terrain features and in cross-loaded gullies.

Aspects:

North, North East, East, South East, South.

Elevations:

Alpine, Treeline.

Storm Slabs

An icon showing Storm Slabs

Likelihood

Possible

Expected Size

2 - 5
Watch for touchy storm slabs on steep unsupported terrain features.

Aspects:

All aspects.

Elevations:

All elevations.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible

Expected Size

3 - 7
More likely to be triggered from thin slab areas, from heavy triggers like cornice falls, or from storm or wind slab avalanches stepping down to deeper weaknesses.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Valid until: Jan 6th, 2012 8:00AM