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Avalanche Forecast

Archived

Nov 21st, 2024–Nov 22nd, 2024

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 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, human triggered possible.

Regions

Kootenay Boundary, Lizard-Flathead, Bonnington, Grohman, Kootenay Pass, Norns, Rossland, Ymir, Flathead, Lizard, Crawford, Moyie, St. Mary, Kokanee.

Lots of new snow has increased the avalanche danger.

The best and safest riding will be found on low-angle slopes with no terrain traps below.

Confidence

Low

Avalanche Summary

A large (size 2.5) natural storm slab occurred on Thursday in the Lizard Range. It was on a fan feature below a headwall.

Numerous small, wind slabs were triggered by riders in open areas near Nelson on Wednesday.

A large rider-accidental avalanche was triggered at Harvey Pass, Fernie on Monday. It started as a storm slab and stepped down to the crust near the base of the snowpack.

Snowpack Summary

The top of the snowpack consists of 20 cm of new snow on top of another 30-40 cm from last weekend.
The bottom is moist snow or a crust from early November that is just above the ground. The crust has acted as a bed surface for recent avalanches, it's unclear how long this layer will last.
Snowpack depth is 80-100 cm at treeline.

Weather Summary

Thursday Night

Cloudy with 5 to 10 cm of snow. 10 km/h southwest ridgetop wind. Treeline temperature -3 °C.

Friday

Cloudy with 5 to 10 cm of snow. 10 km/h east ridgetop wind. Treeline temperature -5 °C.

Saturday

Cloudy with 10 to 20 cm of snow. 10 to 20 km/h west ridgetop wind. Treeline temperature -6 °C.

Sunday

Mostly cloudy with 5 to 10 cm of snow. 10 km/h west ridgetop wind. Treeline temperature -6 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for fresh storm slabs building throughout the day.
  • As the storm slab problem worsens, the easy solution is to choose more conservative terrain.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.