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Avalanche Forecast

Archived

Dec 16th, 2012–Dec 17th, 2012

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

Regions

Kootenay Boundary.

Confidence

Fair - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

Overnight and Monday: A Low pressure system is moving into the region from the coast on Sunday evening. This system is expected to bring 15-20 mm of precipitation by late Monday morning. With the cool alpine temperatures, this may be 20-30 cms of light snow at higher elevations. Strong SW winds during the storm are expected to become strong NW after it passes to the East.Tuesday: No precipitation is expected. Alpine temperatures are expected to be -12.0 combined with strong NW winds.Wednesday: Continued dry and cold in the morning with light winds. In the afternoon or evening the next system should move in from the coast.

Avalanche Summary

No new avalanches reported. Some sluffing from steep terrain in the Kootenay Pass area.

Snowpack Summary

New snow combined with light winds formed some very soft slab on all aspects. The recent storm snow has not consolidated into a slab. Forecast strong winds and more new snow should create storm slabs on all aspects and at all elevations. The late November surface hoar layer that is buried down about 50 cms may be reactive in the Rossland Range with added load from the storm.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.