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Avalanche Forecast

Archived

Nov 29th, 2011–Nov 30th, 2011

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 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

Fair - Due to limited field observations

Weather Forecast

Wednesday: Clearing is expected as the low pressure system that was dominating our weather slides east into Alberta. Freezing levels will rise to over 1300m during the day under clear skies and return to valley bottom at night.Thursday: Expect a few clouds with temperatures tapping out around -2 C @ 1500m. Freezing levels will rise to around 500 m. Winds in the alpine will be at 20 – 35 km/hr out of the northwest. Winds die down as you drop in elevation; expect light winds out of the south west @ treeline.

Avalanche Summary

No current avalanche observations from the field. I suspect there may have been a natural cycle later Sunday into Monday as the last storm came through. At this point we have extremely limited observations from the Kootenay-Boundary region. 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 -150cms. There are locations in the alpine that have just over 200cm. 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 snowpack above. There have been evidence large avalanches running to ground in surrounding regions last Friday. I suspect this may have also occurred in the Kootenay Boundary but have no solid evidence. We should keep this layer in the back of our minds as we move forward. Sunday's big system produced but a few centimeters 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. 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.