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Avalanche Forecast

Archived

Dec 8th, 2021–Dec 9th, 2021

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

Regions

Cariboos.

Danger will remain elevated at upper elevations due to strong westerly winds. Some uncertainty remains about buried weak layers, so travel with extra caution.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Unsettled weather until the next storm arrives on Saturday.

WEDNESDAY NIGHT: Partly cloudy with some scattered flurries brining 1-5 cm of snow, strong wind from the southwest with gusts to 60 km/h, treeline temperatures drop to -12 C.

THURSDAY: Mix of sun and cloud with some scattered flurries bringing up to 5 cm of low density snow, moderate wind from the west with gusts to 50 km/h, treeline temperatures around -10 C.

FRIDAY: Mix of sun and cloud with some scattered flurries bringing up to 5 cm of snow, strong wind from the southwest with gusts to 70 km/h, treeline temperatures reach -8 C.

SATURDAY: Periods of snow with 10-20 cm by the afternoon, strong to extreme wind from the south, treeline temperatures reach -5 C.

Avalanche Summary

We expect strong wind and new snow to have caused some avalanche activity in the alpine on Wednesday.

There were two human triggered avalanches involving old snow earlier this week. One was a size 2 avalanche triggered in a north-facing bowl near Barkerville. This avalanche is suspected to have occurred on a 50 cm deep surface hoar layer that our field team also observed in that area. The other was triggered near McBride and released on a steep rocky slope near treeline (see this MIN report). The failure layer was likely an early season crust/facet layer.

Snowpack Summary

Recent storms delivered 30-50 cm of low density snow. There are a few potentially concerning layers underneath this snow including isolated layers of surface hoar around treeline and a slippery crust below 1800 m. The snow at higher elevations has been heavily impacts by wind, with scoured surfaces on windward terrain and wind slabs on leeward terrain. Regardless of the elevation, be alert to areas where the recent snow feels stiff or slabby.

An early season crust layer with some weak snow around it can be found 100-250 cm deep in the alpine, but may be more shallowly buried in some terrain. There is also evidence of a weak surface hoar layer 50 cm deep in the Barkerville area.

Terrain and Travel

  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Caution around convexities or sharp changes in terrain.
  • Avoid areas where the snow feels stiff and/or slabby.
  • Be alert to conditions that change with elevation and wind exposure.

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.