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Avalanche Forecast

Archived

Dec 11th, 2013–Dec 12th, 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

Thursday: Light snowfall / Moderate to strong westerly winds / Freezing level at valley bottomFriday: Flurries / Moderate northwesterly winds / Freezing level at 1000mSaturday: Light snowfall / Moderate southerly winds / Freezing level at 1000m

Avalanche Summary

Small wind slab avalanches have been observed at treeline and in the alpine around Nelson and in the Kootenay Pass area.

Snowpack Summary

Dribs and drabs of recent snowfall now overlie generally faceted surfaces that formed during the recent cold snap. At the same buried interface you may find small surface hoar on sheltered slopes or windslabs in exposed alpine terrain. Between 50 and 70cm below the surface you may find a weak layer of surface hoar on sheltered north facing slopes and a crust on steep solar aspects. In some areas the overlying snowpack has not yet settled into a cohesive slab required for significant propagation. 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. Little is known about its reactivity in this region.

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.