Avalanche Canada jlammers, Avalanche Canada

Sea to Sky Avalanche Forecast

Dec 19th, 2012 9:01AM

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

Summary

Confidence

Fair - Due to variable weather conditions

Weather Forecast

Moderate to heavy snowfall is forecast for Wednesday and possibly into Thursday with strong to extreme southwest winds. A mix of sun and cloud, reduced winds and intermittent flurries are forecast for Friday and Saturday. Daytime freezing levels area expected to remain at about 600m for the forecast period.

Avalanche Summary

Soft slab avalanches to size 1.5 were reported from the region on Tuesday. They formed in response to recent wind and snowfall. Expect ongoing storm slab avalanche activity with snow and wind forecast for Wednesday night.

Snowpack Summary

Expect widespread storm slab and wind slab formation in the wake of weather forecast for Wednesday. This will add to the 40-80 cm of recent storm snow that has been shifted into wind slabs on slopes lee to SE to SW winds. A couple of layers of surface hoar were buried last week in some areas. Snowpack test results on the surface hoar suggest an improving bond. The mid-pack is reported to be well settled and strong. A deeper layer of surface hoar from late November has been found intact or decomposing in some locations down a metre or more. The early November crust/facet combination near the base of the snowpack seems to be dormant. Triggering one of these persistent weak layers from a shallow snowpack area, or with a heavy trigger, remains possible.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Likely

Expected Size

1 - 4
New snow and strong winds are likely to create widespread instabilities. Be alert for wind slabs behind ridges and ribs. Soft slabs or sluffs can be found on steep terrain sheltered from the wind.
Be cautious as you transition into wind affected terrain.>Assess start zones carefully and use safe travel techniques.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Dec 20th, 2012 2:00PM