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Avalanche Forecast

Archived

Dec 9th, 2023–Dec 10th, 2023

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.
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.

Storm snow remains triggerable at higher elevations. Uncertainty around a buried weak layer is best managed through conservative terrain choices.

Confidence

Moderate

Avalanche Summary

Many storm slab and loose wet avalanches released during the intense rainy conditions earlier this week. Natural avalanche activity likely tapered on Friday.

We're uncertain on whether avalanches could still release on the surface hoar layer described in the Snowpack Summary, so travelling cautiously until there is evidence it is bonding is a good strategy.

Snowpack Summary

20-50 cm of snow sits on a melt-freeze crust. Below, the moist snowpack is slowly refreezing from the top down.

A weak layer of surface hoar buried 50 cm deep has been observed to have miraculously survived the rain. With plenty of uncertainty, we think that it may have been largely cleaned out by avalanches during the storm, but lingers in isolated features. As the overlying crust becomes thicker and more supportive, the bridging effect will reduce the likelihood of triggering this layer, where it exists. In the meantime, we recommend treating this layer as suspect while we await more observations.

Snowpack depths are generally 60-110 cm at treeline, tapering quickly with elevation.

Weather Summary

Saturday night

5-15 cm of new snow. Moderate to strong southerly wind. Freezing level valley bottom.

Sunday

2-5 cm of new snow. Moderate southwest wind. Treeline high temperature around -2. Freezing level 900 m.

Monday

Mix of sun and cloud. Light northwest wind. Treeline high temperature around -2. Freezing level 900 m.

Tuesday

Mix of sun and cloud. Light to moderate southwest wind. Treeline high temperature around -3. Freezing level 600 m.

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.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Uncertainty is best managed through conservative terrain choices at this time.
  • 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.