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Avalanche Forecast

Archived

Dec 4th, 2013–Dec 5th, 2013

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

Regions

Kootenay Boundary.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Mostly clear and cold for the forecast period. There is a chance of some cloud and very light flurries in the Southeast.

Avalanche Summary

No reports of natural avalanches releasing after the storm. Storm slab avalanches may continue to be triggered by light additional loads like skiing/riding. Storm slab avalanches that are released may be large and destructive. This storm needs some time to settle and bond, forecast cold temperatures may preserve recently buried weak layers and require more time to settle and bond than when the post storm temperatures are warm. This is a complex avalanche forecasting scenario; complicated by early season timing when we have few observations coming from the field.

Snowpack Summary

The new storm slab is about 40-70 cm deep depending on where you are in the region. Storm slabs are sitting above recently buried weak layers of surface hoar on North aspects and melt/freeze crusts on solar aspects. In some parts of the region, the storm slab may not be well consolidated and may not result in shears from snow-pit tests. There are some 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.