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Avalanche Forecast

Archived

Nov 28th, 2011–Nov 29th, 2011

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

Regions

Kootenay Boundary.

Confidence

Poor - Due to limited field observations

Weather Forecast

Light to moderate precipitation is forecast for tuesday afternoon with moderate southwest winds and freezing levels reaching 1200m.On wednesday and thursday a ridge is expected to dominate the area bringing clear skies, light to moderate northwest winds and freezing levels at or near surface.

Avalanche Summary

Numerous size 3 natural avalanches were reported north of the region on friday on a suspected early season crust that has been reactive in a few regions throughout the province. At this point we have extremely limited observations from the Kootenay-Boundary region; but the recent weather has been sufficient to produce significant avalanche activity at treeline and in the alpine. If you have any avalanche observations to report, please email us at: [email protected].

Snowpack Summary

Generally there is about 150 cms in the alpine, and treeline has been showing some variability between 50 -150 cms. There are locations in the alpine that have 200 cms plus already. On friday we received new information from the Selkirks south of Revelstoke that there was indeed a major avalanche cycle up to size 3.5 during the last storm, but it appears that most of the avalanches were sliding on a layer that is near the ground; perhaps a rain crust from October. This crust has also been highly reactive in the Lizard Range to the east. At this point we have heard no reports of this lower layer existing in the Kootenay-Boundary region; however, I think that we should at least be curious about the possibility of its existence as we gather information from data-sparse areas.Sunday's big system produced but a few centimetres of snow with freezing levels rising to 1800m, but winds were strong from the southwest. In the mid and upper snowpack, expect wind slabs and storm slabs resulting from this wind event and last weeks storms. With tuesday's forecast snow and wind, expect further wind and storm slab development.We hope to get some more information soon, as operators start getting out into the field. Any info from the field is welcome in our office. Let me know what you're seeing out there! [email protected]

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.

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.