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Avalanche Forecast

Archived

Dec 10th, 2019–Dec 11th, 2019

Alpine
Natural avalanches unlikely, human triggered possible.
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.

Triggering storm slab avalanches is possible. Watch out for signs of instability as you approach avalanche terrain.

Confidence

Moderate - Uncertainty is due to the complexity of the snowpack’s structure.

Weather Forecast

TUESDAY NIGHT: Cloudy with flurries, up to 5 cm of snow, 30 km/h wind from the southwest, alpine temperature around -4 C, freezing level at 800 m. 

WEDNESDAY: Cloudy with isolated flurries, 30 km/h wind from the west, alpine high temperatures around -6 C, freezing level at 1000 m.

THURSDAY: Cloudy, up to 15 cm of snow, 50 km/h wind from the southwest, alpine high temperatures around -4 C, freezing level at 1000 m.

FRIDAY: Cloudy with isolated flurries, light wind from the west, alpine high temperatures around -7 C, freezing level at 900 m.

Avalanche Summary

On Monday, a few slab avalanches up to size 2.5 were triggered with explosives. They were up to 30 cm thick and released on a crust on eastern to southerly aspects. 

On Sunday, numerous small natural avalanches (size 1) were observed on east aspects. A few skier triggered avalanches of size 1-2 were reported. On Saturday, several slab avalanches of size 1-2 were triggered by skiers. Two artificially controlled avalanches of size 1 and 2 were reported. Some of these slabs were up to 50 cm thick and released on a crust. They occurred on all aspects. Avalanches of smaller size released within the recent storm snow.

Snowpack Summary

The past week delivered about 15-60 cm of snow, with the highest accumulations in the east of the region. This snow has been blown around by southwest wind and sits above hard layers of wind pressed snow and crusts. There are reports of several layers 30-90 cm below the surface that could develop into avalanche problems in the future. These layers could be composed of facet/crust layers or surface hoar depending on aspect and elevation. Several notable snowpack test results and avalanches were reported on these layers. Snowpack depths are about 120 cm at treeline and below treeline is just reaching threshold depths.

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.