Avalanche Forecast

Issued: 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.

ccampbell, Avalanche Canada

Sea To Sky.

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

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.

Likelihood

Possible - Likely

Expected Size

1 - 5

Storm Slabs

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.

Likelihood

Possible

Expected Size

1 - 6

Cornices

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.

Likelihood

Possible

Expected Size

1 - 6

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