Avalanche Forecast

Issued: Dec 14th, 2015 9:14AM

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

jlammers, Avalanche Canada

Northwest Coastal.

You don't have to be an avalanche expert to submit to the MIN. If you've been out in the mountains, we'd love to know what you've seen.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Tuesday

Weather Forecast

A Pacific frontal system will slide through the region on Monday night and Tuesday bringing up to 15cm of snow and strong to extreme westerly winds. A dry ridge of high pressure will develop for Wednesday and early Thursday delivering mainly clear skies and moderate northwesterly winds. Light snowfall is forecast for Thursday afternoon. Freezing levels may rise to 500m with the passage of the frontal system, and then drop to valley bottom on Wednesday and Thursday. For a more detailed weather overview, please check-out our Mountain Weather Forecast at: avalanche.ca/weather

Avalanche Summary

In recent days small pockets of wind slab were observed failing naturally with minimal propagation in the lee of alpine ridge crests. Wind and snow forecast for Monday night and Tuesday will likely spark a new round of wind slab activity in the alpine and at treeline.

Snowpack Summary

Up to 15cm of new snow and strong westerly winds on Monday night are expected to form new wind slabs at treeline and in the alpine. Up to a meter below the surface you may find a weak layer of buried surface hoar. In some areas, this layer may be primed for 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. I'd also be increasingly cautious on sheltered slopes at or below treeline.

Problems

Wind Slabs

Wind and snow forecast for Monday night will form 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.

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, South.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

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

Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.>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 - 4

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