Avalanche Forecast

Issued: Dec 18th, 2014 8:02AM

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

rbuhler, Avalanche Canada

South Columbia.

Conditions will change rapidly as we enter the weekend. Watch for sluffing from steep terrain at all elevations and for signs of early wind slab development in the alpine.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The first wave of precipitation is expected to reach the interior late Thursday night or early Friday morning. 10-20cm of new snow is expected for Friday. Freezing levels are expected to be 1200-1500m and alpine winds moderate to strong from the SW. A weak ridge will keep Friday night and Saturday morning mainly dry before the next storm front arrives on Saturday afternoon or evening. Freezing levels on Saturday will rise to around 1500m or so and alpine winds will increase to strong from the SW. Saturday night and Sunday should yield another 20-40cm of snowfall up high. Freezing levels on Sunday may rise as high as 2000m and winds will remain strong.

Avalanche Summary

An early report on Thursday suggests the new snow is sluffing fast on the surface hoar/crust interface. With another 10-20cm expected overnight, these sluffs may be big enough by tomorrow to knock you off your feet. Caution to steep slopes and terrain traps.

Snowpack Summary

The new snow sits on a layer of large surface hoar. Up to around 2100m elevation this surface hoar sits on a hard rain crust. Above 2100m the surface hoar sits on well settled and faceted snow. As wind increases with the progression of the storm, wind slabs are expected to form in leeward features. A thick rain crust with facets from early November is buried over 1 m down and may still be reactive in isolated areas.

Problems

Loose Dry

The new snow will form a poor bond with the crust/surface hoar interface and fast sluffing is expected from steep terrain. Watch for early stages of wind slab development in the alpine.

Be cautious of sluffing in steep terrain.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

The likelihood of triggering a deep persistent slab has decreased but the consequences remain very high. Be wary of any slopes that did not release during the storms. Heavy triggers such cornice falls may be able to trigger a deep weak layer.

Avoid shallow snowpack areas where triggering is more likely.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely

Expected Size

2 - 5

Valid until: Dec 19th, 2014 2:00PM