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Avalanche Forecast

Archived

Dec 6th, 2023–Dec 7th, 2023

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 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, Bonnington, Grohman, Kootenay Pass, Norns, Rossland, Ymir, Crawford, Moyie, St. Mary, Kokanee, Retallack, Valhalla, Whatshan.

Travel cautiously and assess for slab conditions within the new snow.

Confidence

Moderate

Avalanche Summary

Many storm slab and loose wet avalanches were observed during the stormy conditions over the past few days. Most avalanches were small to large (size 1 to 2). We expect to hear about more avalanche observations once the skies clear.

Going forward, new storm slabs could form from Wednesday night's snow. We're uncertain on whether avalanches could still release on the surface hoar layer described in the Snowpack Summary, so travelling cautiously for now is a good strategy.

Snowpack Summary

Snow will accumulate Wednesday night along with a freezing level decline. Upwards of 30 cm could be found near the mountain tops, with substantially lower amounts expected below treeline. This snow will rest on a wet upper snowpack from this week's intense rain. All of this has loaded a buried weak layer of surface hoar, which has likely avalanched or been squashed out.

The lower snowpack is likely moist where the rain penetrated it. At high elevations, the lower snowpack may still be dry and faceted with a hard melt-freeze crust 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

Wednesday Night

Cloudy with 15 to 30 cm of snow but rain at low elevations, west alpine wind 20 to 30 km/h, treeline temperature -2 °C, freezing level 1900 m dropping to 1300 m by morning.

Thursday

Mostly cloudy with 5 to 10 cm of morning snow, northwest alpine wind 10 to 20 km/h, treeline temperature -5 °C.

Friday

Mix of sun and cloud with no precipitation, northwest alpine wind 10 to 20 km/h, treeline temperature -8 °C.

Saturday

Increasing cloud with 2 to 5 cm of afternoon snow, South alpine wind 20 to 40 km/h, treeline temperature -10 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Closely monitor how the new snow is bonding to the old surface.
  • Early season avalanches at any elevation have the potential to be particularly dangerous due to obstacles that are exposed or just below the surface.
  • Be cautious of buried obstacles especially below treeline.

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.