Avalanche Forecast

Archived

Dec 5th, 2023–Dec 6th, 2023

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

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 unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Kootenay Boundary, Bonnington, Grohman, Kootenay Pass, Norns, Rossland, Ymir, Crawford, Kokanee, Retallack, Valhalla, Whatshan.

Travel in avalanche terrain is not recommended during this warm and intense storm. A natural avalanche cycle may be ongoing.

Confidence

High

Avalanche Summary

Explosives triggered large wet loose avalanches on Tuesday. We expect that a natural avalanche cycle occurred on the buried weak layer of surface hoar described in the Snowpack Summary but we will have to wait for clearing skies for further observations. Continuing stormy conditions may continue this natural cycle wherever the weak layer remains intact.

Snowpack Summary

Stormy conditions continue with a high freezing level. Rain has soaked most of the snowpack to the mountain tops, which will switch to snow as the freezing level drops. This is loading between 10 to 30 cm of snow that overlies a touchy weak layer of feathery surface hoar. The intense storm is likely triggering many avalanches on this layer and perhaps squashing the layer elsewhere, but it may still linger in specific locations.

The remainder of the snowpack is generally weak and faceted, with a hard melt-freeze crust found near the base of the snowpack.

Snowpack depths are generally between 50 and 80 cm at treeline, which quickly tapers as you lower with elevation.

Weather Summary

Tuesday Night

Cloudy with 15 to 30 mm of rain or heavy snow near the mountain tops. Southwest alpine wind 20 to 40 km/h. Treeline temperature 1 °C. Freezing level 2300 m.

Wednesday

Cloudy with 15 to 30 cm of heavy snow or rain below the snow-rain line. Southwest alpine wind 20 to 30 km/h. Treeline temperature 0 °C. Freezing level 1900 m.

Thursday

Mostly cloudy with 5 to 15 cm of early-morning snow. West alpine wind 10 km/h. Treeline temperature -5 °C.

Friday

Mostly cloudy with 2 to 5 cm of snow. West alpine wind 10 to 20 km/h. Treeline temperature -7 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid avalanche terrain during periods of heavy rain.
Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
Early season avalanches at any elevation have the potential to be particularly dangerous due to obstacles that are exposed or just below the surface.

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 Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.