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Avalanche Forecast

Archived

Dec 10th, 2013–Dec 11th, 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 - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The cold arctic air will slowly be replace by relatively warmer air in the next few days as a Pacific frontal system moves onto the coast and inland.Wednesday:  Light flurries,  ridge top temperatures -5 to -10, winds light to moderate from the south southwest, freezing level at valley bottom.Thursday:  Light to locally moderate precipitation, freezing levels at valley bottom, ridge top temperatures -5 to -10

Avalanche Summary

Small natural wind slab 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 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. In the alpine and at some tree line locations the snow has been redistributed by the recent north to east winds forming wind slabs at ridge-top and cross loading some 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.