Avalanche Forecast

Archived

Dec 10th, 2023–Dec 11th, 2023

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.

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

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

No new avalanches were reported this weekend.

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 travel cautiously until there is evidence it is bonding or has been destroyed.

Snowpack Summary

25-50 cm of snow sits on a 3-15 cm melt-freeze crust. Below, previously moist snow from the rain event seems to have mostly refrozen.

A layer of surface hoar buried ~45 cm has been observed to have miraculously survived the rain in some areas. It may have been largely cleaned out by avalanches during the recent storm, but could linger in isolated features. Triggering this layer is less likely in areas where the overlying crust is thicker and more supportive. We recommend treating this layer as suspect while we await more observations.

Snow depth is generally 70-110 cm at treeline, tapering quickly below. The mid and lower snowpack may contain a weak facet layer in shallower areas.

Weather Summary

Sunday Night

Cloudy. 5-7 cm of new snow. Light to moderate southwest ridgetop wind. Treeline high temperature around -6°C.

Monday

Partly cloudy. No new snow expected. Light north ridgetop wind. Treeline temperature around -5°C.

Tuesday

Mix of sun and cloud. No new snow expected. Light to moderate southwest ridgetop wind. Treeline temperature around -4°C.

Wednesday

Mix of sun and cloud. No new snow expected. Moderate to strong south ridgetop wind. Treeline temperature around -6°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.
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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.