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Avalanche Forecast

Archived

Nov 26th, 2014–Nov 27th, 2014

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

Regions

South Columbia.

Winter storm conditions have produced a dangerous storm slab which sits on a touchy weak layer.  Now is a good time to avoid avalanche terrain and stick to low angle slopes.

Confidence

Fair

Weather Forecast

A warm, moist Pacific storm will continue to bring moderate-heavy precipitation to the southern interior on Thursday. An Arctic high pressure system should arrive on Friday morning bringing cold, sunny conditions for the weekend. Weds. Night/Thursday: Precipitation 15-25mm, freezing level around 2000m, ridgetop wind strong SW Thurs. Night: Precipitation 6-12mm, ridgetop wind strong SWFriday: A mix of sun and cloud, light flurries possible, freezing level valley bottom, ridgetop wind easing during the daySaturday: A mix of sun and cloud, treeline temperature around -10C, ridgetop wind calm

Avalanche Summary

On Monday and Tuesday, explosive control at a ski area produced widespread storm slabs up to size 2. On Tuesday, Glacier National Park reported numerous natural avalanches up to size 3. Observations are still very limited but it is expected that avalanche activity is occurring throughout the region. As new snow continues to accumulate, natural avalanche activity is expected to continue and the size of these avalanches will continue to increase.

Snowpack Summary

Around 80-100cm of recent storm snow sits on the mid-November drought layer (facets, surface hoar, and/or a sun crust on steep southerly slopes). 20-30cm below this layer is a thick rain crust with weak facets on top. In the Rogers Pass area, the storm slab is poorly bonded to the mid-November layer and snowpack tests suggest it can be triggered easily with wide propagations possible. In some tests, the deeper crust/facet layer was also failing and it is possible that avalanches may step down to this layer.Check out Parks Canada Mountain Safety Facebook Page for a couple videos of their snowpack tests on Tuesday.Recent strong and variable winds have created wind slabs in exposed terrain and resulted in variable snow distribution in the alpine. At lower elevations expect travel to be difficult and potentially hazardous as many early season hazards are exposed or lightly buried (stumps, logs, rocks, open creeks, etc).

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.