Avalanche Forecast

Issued: Dec 15th, 2012 9:06AM

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

triley, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain on Monday

Weather Forecast

Overnight and Sunday: Moderate westerly overnight winds combined with 3-5 cms of new light snow is expected by Sunday morning. Alpine temperatures should be -10.0 and the freezing level is expected to remain at valley bottom for the forecast period.Monday: The Low pressure system that is tracking along the U.S border should bring some precipitation and strong Southwest winds to the region. The South of the region may get 10-15 cms and the North should get less; likely 5-10 cms.Tuesday: Unsettled weather and cooler temperatures are expected after the storm passes to the East. Forecast alpine temperatures are -15.0.

Avalanche Summary

Some thin soft slab avalanches up to size 1.5 were reported from ski cutting that were 20 cms deep.

Snowpack Summary

Some new surface hoar has been reported overnight. Thin windslabs have developed in the alpine and at treeline in exposed terrain. Some loose snow sluffing may be experienced in steep terrain. Snow pit test results continue to show weak layers of surface hoar that was buried during mid and late November, however we have not seen any activity on these layers recently. The early season rain crust is another layer that continues to show results in tests, but has not been active.

Problems

Wind Slabs

Thin new windslabs have developed in the alpine and at treeline.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Travel on ridgetops to avoid wind slabs on slopes below.>Stay well to the windward side of corniced ridges.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Persistent Slabs

Buried surface hoar layers continue to give results in snow pit tests. This layer may be triggered from thin weak spots on or adjacent to unsupported terrain features.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Deep Persistent Slabs

Avalanche activity on the deeply buried November rain crust is un-likely without new loading or a rapid rise in temperature. Avalanches that do release on this layer will be large and destructive.

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

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely

Expected Size

3 - 7

Valid until: Dec 16th, 2012 2:00PM