Avalanche Forecast

Issued: Dec 15th, 2015 8:20AM

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.

jlammers, Avalanche Canada

Northwest Coastal.

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Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Mainly clear skies are forecast for Wednesday and Thursday morning. Increased cloud is expected throughout the day on Thursday with 5-15cm of new snow falling between Thursday afternoon and Friday morning. Ridgetop winds should be light to moderate from the north on Wednesday, switching to strong and southwesterly with Thursday's snowfall. Freezing levels should hover around valley bottom for the forecast period. For a more detailed weather overview, check-out our Mountain Weather Forecast at: avalanche.ca/weather

Avalanche Summary

At the time of publishing this bulletin, there were no new reports of avalanche activity. I'm sure there was a round of new wind slab activity on Tuesday in response to new snow and strong winds. New wind slabs may remain sensitive to human triggering for longer than normal due to the presence of underlying surface hoar.

Snowpack Summary

On Monday night, between 18cm (in the north) and 26cm (in the south) of new snow and strong variable winds formed new wind slabs at treeline and in the alpine. Below the new snow, you may find a layer of surface hoar. I'd keep an eye on this layer as the overlying slab gets deeper and gains cohesion. Up to a meter below the surface you may find another layer of buried surface hoar. In some areas, this layer may be sensitive to human triggering and wide propagations while in other areas it is non-existent or has gained significant strength. Due to the variable nature of this weak layer, I'd dig down to test for it before committing to any steep lines on slopes at or below treeline.

Problems

Wind Slabs

Wind and snowfall on Monday night has likely formed new wind slabs in the alpine and at treeline. Watch for conditions that change with elevation, and use extra caution around ridge crests, gullies and convexities.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Human triggered avalanches on a layer of buried surface hoar have become unlikely. However, avalanches at this interface could be destructive in nature. Dig down and test for this weakness before committing to any steep, exposed lines at treeline.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 16th, 2015 2:00PM