Avalanche Forecast

Issued: Dec 11th, 2012 9:09AM

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

pgoddard, Avalanche Canada

Northwest Inland.

Summary

Confidence

Poor - Due to limited field observations

Weather Forecast

Wednesday: Light NW winds. Alpine temp -7. Light to moderate snow beginning late in the day.Thursday: Strong to gale W winds. Alpine temp -8. Moderate snow.Friday: Light S winds. Alpine temp -8. Moderate snow.

Avalanche Summary

Strong W-NW winds triggered a natural avalanche cycle on Sunday, with several slabs to size 2 failing behind cross-loaded ribs and gullies. A size 2.5 slab from the headwall above the Hankin-Evelyn area is suspected to have failed on the Nov crust/facet layer. We have no reports of avalanches during Monday night’s warming, but I wouldn’t be surprised if a natural cycle had occurred.

Snowpack Summary

Warm temperatures on Monday night led to upside-down storm snow (dense snow over lighter snow) and rain at low elevations. Wind slabs formed in the last few days may now be buried on a variety of slopes. In the upper snowpack, surface hoar is buried at tree line in isolated sheltered areas. A November crust/facet layer near the base of the snowpack has the potential for deep releases. Snow depths are highly variable due to the influence of recent winds.

Problems

Wind Slabs

Wind slabs are likely to be found on alpine slopes and behind ridges and ribs at treeline. Storm slabs may exist in sheltered areas not affected by wind.

Be cautious as you transition into wind affected terrain.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Deep Persistent Slabs

A deeply buried facet/crust weakness exists. While the likelihood of triggering is relatively low, the consequences could be a very large and destructive avalanche.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Dec 12th, 2012 2:00PM