Avalanche Forecast

Archived

Dec 4th, 2023–Dec 5th, 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 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.

Regions

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

Travel in avalanche terrain is not recommended during the intense storm. A natural avalanche cycle is likely to occur.

Confidence

High

Avalanche Summary

Riders observed small slab avalanches on Sunday, failing on the weak layer of surface hoar described in the Snowpack Summary. Check out this MIN for an example.

Avalanche activity is expected to be widespread on Monday night and Tuesday as the weak snowpack is rapidly loaded by snow and rain.

Snowpack Summary

An intense storm will impact the region Monday night and Tuesday, first bringing snow that will quickly switch to rain. This will build on and soak the 20 to 30 cm of snow that overlies a touchy weak layer of feathery surface hoar. Storm slabs are expected to be very touchy to riders with rapid slab development and loading over this weak layer.

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, with substantially lower amounts as you lower with elevation.

Weather Summary

Monday Night

Cloudy with snow switching to rain below approximately 2500 m, accumulation 10 to 20 cm of snow possible at the highest elevations. Southwest alpine wind 40 km/h. Treeline temperature 1 °C. Freezing level rising from 1000 m to 2500 m.

Tuesday

Cloudy with heavy rain or snow, 15 to 30 cm snow accumulation possible at the highest elevations above the rain-snow line. Southwest alpine wind 20 to 40 km/h. Treeline temperature 1 °C. Freezing level 2500 m.

Wednesday

Cloudy with rain or snow, 20 to 40 cm snow accumulation possible above the rain-snow line. Southwest alpine wind 20 to 40 km/h. Treeline temperature 1 °C. Freezing level 2100 m.

Thursday

Mostly cloudy with 10 to 20 cm of early-morning snow. Northwest alpine wind 20 km/h. Treeline temperature -5 °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.