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Avalanche Forecast

Archived

Nov 30th, 2011–Dec 1st, 2011

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

Regions

Kootenay Boundary.

Confidence

Fair - Due to limited field observations

Weather Forecast

A substantial upper ridge over the interior will bring dry, conditions under a cool northwesterly flow. Ridgetop winds on Thursday will be 30-40km/h from the northwest. Alpine temperatures will sit at -6 degrees, with the freezing level rising to 900m then dropping back to valley bottom at night. Friday through the weekend we can expect similar conditions with light-moderate winds in the alpine, and clear sunny skies.

Avalanche Summary

Up to 20cm of new snow fell over Tuesday night. With the clear sunny skies on Wednesday, the solar radiation kissed the southerly slopes producing size 1.0, loose moist avalanches. These were small and relatively harmless. I suspect we may see more of this during the sunny days to come. If you have any avalanche observations to report, please email us at: [email protected].

Snowpack Summary

Sunday's big system produced but a few centimeters of snow with freezing levels rising to 1800m, but winds were strong from the southwest forming wind slabs on lee slopes and terrain features. Generally there is about 150-200cm in the alpine, and treeline has been showing some variability between 50 -150cms. Recent snow pack observations are indicating the late October rain crust is present in the alpine elevations and down approximately 120cm. This crust is said to be up to 5mm in thickness with predominate faceting below it. For the moment the crust seems to be bridging over the facets below, with a settling, bonding snowpack above. There has been evidence of large avalanches running to ground in surrounding regions last Friday. I suspect this may have also occurred in areas of the Kootenay Boundary but have no solid reporting evidence. We should keep this layer in the back of our minds as we move forward.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.