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Avalanche Forecast

Archived

Dec 12th, 2023–Dec 13th, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

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

There is still uncertainty with where persistent slabs may still be reactive after last week's rain event. Be sure to post observations on the Mountain Information Network.

Confidence

Moderate

Avalanche Summary

There are no new avalanches to report in past few days.

Snowpack Summary

30-55 cm of snow sits on a 5-15 cm melt-freeze crust. Below this crust you may find moist snow to ground, or dry, possibly refrozen snow and a layer of somewhat preserved surface hoar around 60 cm deep.

Triggering this layer of surface hoar may be possible in areas where the overlying crust is thinner and less 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

Tuesday Night

Mainly Cloudy. Light west ridgetop wind. Treeline temperature around -8 °C, with possible temperature inversion in the alpine.

Wednesday

Mainly sunny. Moderate southwest ridgetop wind. Treeline temperature around -3°C, with possible temperature inversion in the alpine.

Thursday

Mostly cloudy. Isolated flurries with 1-3 cm accumulation. Moderate to strong southwest ridgetop wind. Treeline temperature around -4°C.

Friday

Mainly cloudy. Moderate southwest ridgetop wind. Treeline temperature -5°C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • 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

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.