Avalanche Forecast

Issued: Dec 14th, 2015 8:48AM

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

jfloyer, Avalanche Canada

South Rockies.

Windslabs in exposed areas could exist on both North and South aspect slopes.Low probability, but there is still a chance of tickling a buried weak layer at lower treeline elevations.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

On Tuesday: dry, mostly light winds from the north and freezing levels at valley bottom.Â On Wednesday: 3-8 cm new snow, light northeasterly winds, freezing levels at valley bottom. On Thursday: current models indicate a dry day, with light or moderate southerly winds and freezing levels remaining at valley bottom.

Avalanche Summary

On Monday, a couple of size 2 avalanches were reportedly triggered by skiers in steep north and northeast facing slopes. Over the weekend, explosives and ski cutting produced storm slabs size 1-2 which were typically 20-60cm thick.

Snowpack Summary

The series of storms last week produced 70-90cm of new snow in the region. A rain crust which formed during the middle of the storm is now down 40-60cm and has become the primary layer of concern during the weekend storm. The early December interface consists of crust, surface hoar, and/or facets and is typically down 70-90cm. Around 20-30cm below this interface is a rain crust from mid-Nov with a thick layer of facets below it. Both the early-Dec and mid-Nov layers have become dormant and are likely being capped at treeline and below by the more recent rain crust layer. However, these layers may still be reactive to heavy triggers such as cornices, explosives, or smaller avalanches stepping down.

Problems

Wind Slabs

Wind slabs may exist on northerly aspects as well as southerly aspects as the wind has shifted round to the north.

Avoid freshly wind loaded features.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

A weakness buried early-Dec and a rain crust from mid-Nov in the mid-pack are becoming difficult to trigger but are still a concern in isolated areas. Heavy triggers like cornices or avalanches stepping down could result in very large avalanches.

Caution around convexities or areas with a thin or variable snowpack.>Avoid open slopes and convex rolls at and below treeline where persistent weaknesses may be preserved.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Dec 15th, 2015 2:00PM