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Avalanche Forecast

Archived

Jan 7th, 2012–Jan 8th, 2012

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

Regions

Northwest Inland.

Confidence

Fair - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

A very strong moist southwest flow is expected to bring about 40 cm of new snow to higher elevations in near coastal areas by Saturday night. Expect winds up to 120 km/hr and freezing levels around 1000 metres rising rapidly to near 1500 metres by Saturday evening. The wind is forecast to moderate to about 60 km/hr by Sunday morning and the freezing level should drop back down to about 1000 metres. There is another heavy pulse of precipitation on Sunday that looks like it will be focused on the area South of Kitimat. This system is forecast to bring another 20 cm of snow to higher elevations around Terrace. If this system moves a little further north, Terrace and Bear Pass could see double this amount. The mountainous areas around Smithers are expected to get 15-20 cm by Sunday morning, and another 10-15 cm by Monday morning. Cooler dry air is expected to follow by Monday noon, and continue to influence the Northwest on Tuesday. Freezing levels should be at valley bottoms by Monday night, and we may see cold outflow winds from the northeast by Tuesday.

Avalanche Summary

No new avalanche reports from this region.

Snowpack Summary

The strong southwest wind and snow has begun to develop new windslabs and storm slabs above the recent storm instabilities. There is a rain crust down about 40 cm that exists up to approximately 1000 m. There is now approximately 80 to 120cms of storm snow sitting above a surface hoar/crust/facet layer that was buried mid-December. The increasing depth of this weak layer makes it difficult to trigger. I would not ignore this layer yet, as it could still be triggered by large loads such as rapid loading by new snow or rain or cornice falls. It could also be triggered by riders in shallow snowpack areas or where rocks poke up near the surface. The mid- and lower snowpack layers are well consolidated and generally strong.

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.

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.