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Avalanche Forecast

Archived

Dec 8th, 2013–Dec 9th, 2013

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

Regions

Kootenay Boundary.

Confidence

Fair - Due to the number of field observations

Weather Forecast

An arctic air mass is still sitting over much of BC however a series of fronts will start to drive the cold air out of the region late this week.Monday: Cloudy with sunny periods. Precipitation: Chance of flurries overnight. Alpine temperature: High -20. Ridge Winds: Light west. Freezing level at valley bottom.Tuesday: Cloudy with sunny periods. Precipitation: Nil. Alpine temperatures: High -15, Ridge Winds: Light west. Freezing level at valley bottom.Wednesday: Mainly cloudy.. Alpine temperatures: High -15, Ridge winds: Light south-west. Freezing level at valley bottom.

Avalanche Summary

Small natural windslab avalanches have been observed at treeline and in the alpine around Nelson.

Snowpack Summary

The recent cold temperatures have driven faceting in the upper snowpack and surface hoar growth is being reported in some areas. The snow that fell last week is sitting above a buried weak layer of surface hoar found on north facing slopes and a crust on steep solar aspects. In many places the upper snowpack has not yet settled into a slab. However, in open areas this snow has be redistributed by the recent north to east winds forming windslabs at ridge-top and in cross loaded features. There are reports of a deeply buried early season crust that formed in October, this layer is more likely to be found in the high alpine on northerly aspects.

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.