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Avalanche Forecast

Archived

Dec 14th, 2015–Dec 15th, 2015

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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.

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 Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.