Avalanche Canada ccampbell, Avalanche Canada

Sea to Sky Avalanche Forecast

Apr 4th, 2012 10:39AM

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 Cornices.

Summary

Confidence

Good

Weather Forecast

Thursday: Unsettled conditions with scattered flurries and sunny breaks. Freezing levels around 1000m and light northerly winds. Friday and Saturday: A ridge of high pressure is expected to keep things mainly sunny and dry. Freezing levels are expected to hover around 800-1000m on Friday and slightly rise to 1200m for Saturday. Winds should remain light from the north.

Avalanche Summary

Reports from Tuesday include numerous easily triggered wind and storm slab avalanches up to Size 3. The slabs showed a high propensity to propagate fractures with remote and sympathetic triggers and entire bowls releasing wall-to-wall. Most of the avalanches involved the most recent storm snow, but a few stepped-down over a metre to the crust from late March.

Snowpack Summary

Over 60cm of new snow in the past couple of days was redistributed by strong southwesterly winds into thick wind slabs. A predominately crusty weak interface from late March, now down 50-150cm, remains a potential failure layer for large slab avalanches, especially with heavy triggers such as cornice falls and step-down avalanches. The potential for remote triggering, step down avalanches, and wide propagations, makes the current snowpack structure particularly tricky to manage.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Likely - Possible

Expected Size

1 - 5
Generally lurking below ridgecrests, behind terrain features, and in gullies. Thick fresh wind slabs are highly sensitive to human triggers and cornice falls, and sun-exposure is expected to make things even more touchy.

Aspects:

North, North East, East, South East.

Elevations:

Alpine, Treeline.

Storm Slabs

An icon showing Storm Slabs

Likelihood

Possible

Expected Size

1 - 6
Storm slabs could be easily triggered and have the potential to step-down to deeper weaknesses, especially with solar warming.

Aspects:

All aspects.

Elevations:

All elevations.

Cornices

An icon showing Cornices

Likelihood

Possible

Expected Size

1 - 6
Large and weak cornices could easily start popping off with sun-exposure. Not only are they a hazard in themselves, but can also act as a heavy trigger for very large avalanches on the slope below.

Aspects:

North, North East, East, South East.

Elevations:

Alpine.

Valid until: Apr 5th, 2012 9:00AM