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Avalanche Forecast

Archived

Dec 1st, 2014–Dec 2nd, 2014

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

Regions

South Rockies.

What did you see over the weekend? We welcome your observations. Email forecaster@ avalanche.ca.

Confidence

Poor - Due to the number of field observations

Weather Forecast

Synopsis: Fairly static weather pattern, the arctic high pressure centre persists over Southeastern BC for the next few days. The models suggest that cloud and precipitation will push into the southern half of the province Thursday night/Friday. Tuesday: Freezing Level: Valley Bottom; Precipitation: Nil; Wind: Treeline: Moderate, W/SW | Ridgetop: Strong, NWWednesday: Freezing Level: Valley Bottom; Precipitation: Nil; Wind: Treeline: Light, SW | Ridgetop: Moderate WThursday: Freezing Level: Valley Bottom; Precipitation: Nil; Wind: Treeline: Moderate, SW | Ridgetop: Moderate, W

Avalanche Summary

Explosives triggered two very large (size 2.5 and 3.5) slabs in the south of the region on Thursday around treeline. These failed on a weak layer of facets buried about a week ago. We haven't had any newer reports, but I'd expect some further avalanche activity to occur this weekend in response to the recent snow and wind, with the chance of triggering a deeper weakness and creating a very large event.

Snowpack Summary

As we begin our forecasting season, we are working with very limited field data. If you have been out in the mountains, we'd love to hear from you. Please email us at [email protected].Half a metre or so of recent snow is likely to have been redistributed by wind into fresh slabs on lee slopes. Natural avalanches may continue spilling down steep headwalls for a day or two. A weak layer (of facets over a crust) which formed during November's dry spell is now buried a metre or more down. Avalanches failing on this layer have the potential to propagate widely, leading to very large events.

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.