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Avalanche Forecast

Archived

Dec 29th, 2017–Dec 30th, 2017

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

Regions

Northwest Coastal.

Pockets of reactive wind slab remain a concern for wind-exposed alpine and treeline areas. New snow and wind on Monday will heighten avalanche danger.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SATURDAY: Mostly sunny. Ridge wind moderate west. Temperature -15. Freezing level surface.SUNDAY: Mostly cloudy. Ridge wind light northwest. Temperature -12. Freezing level surface.MONDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind moderate southwest. Temperature -5. Freezing level 400 m.

Avalanche Summary

On Thursday an isolated wind slab release (size 1.5) was observed on an actively wind loading, steep terrain feature in the northern part of the region. And on Sunday, a skier remotely triggered a large wind slab (size 2) near the Shames area. The avalanche was triggered on a steep south-facing rocky ridgetop at 1400 m. Check out the Mountain Information Network (MIN) report here for details. And please post your own observations to the MIN!

Snowpack Summary

The Arctic high remains in place and strong outflow winds have affected the surface snow over the past week, scouring some slopes down to an old crust and forming hard deposits in many other areas. Winds have come from a variety of directions over the past several days and have built wind slabs in much of the alpine and exposed treeline terrain. These wind slabs rest on a variety of old surfaces including a thick melt-freeze crust that formed in mid-December. In some sheltered locations, soft feathery surface hoar crystals may exist on top of this crust. In non-wind affected terrain, 30-40 cm of unconsolidated snow overlies the mid-December crust layer.Beneath the mid-December crust the snowpack is reported to be generally strong with the possible exception of areas around Stewart and northern parts of the region where the late-October, basal crust can be found near the base of the snowpack. Weak sugary snow may exist around this basal crust and could be triggered from shallow snowpack areas.

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.