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Avalanche Forecast

Archived

Feb 21st, 2024–Feb 22nd, 2024

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

Regions

South Coast Inland, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

Seek out soft, sheltered snow for the best quality, safest riding. A wind slab in motion could step down to a deeper weak layer and become surprisingly destructive.

Confidence

Moderate

Avalanche Summary

Over the past week we've seen a pattern of human and remotely triggered, mainly size 1 to 1.5 wind slab avalanches. These avalanches have generally failed on a combination of facets and/or surface hoar sitting on hard crust. Check out this MIN for a recent snapshot of the issue.

Although new snow is shifting some focus away from this older problem, it isn't off the radar. It is adjusting to a new load and the possibility for surface avalanches to trigger it can't yet be ruled out.

Snowpack Summary

15 - 20 cm of new snow from the early art of the week has buried over a variety of previous surfaces including; a crust on south aspects and all aspects at lower elevation, surface hoar in sheltered features, and previously wind-affected surfaces in the open.

Roughly 40 - 50 cm of snow now sits above a widespread crust from late January. Weak grains like facets or more isolated surface hoar may be found above this crust. Old wind slabs that formed above this weak snow remain a concern. Will we see surface wind slabs stepping down to this layer to create larger avalanches?

Snowpack depths decrease rapidly below treeline.

Weather Summary

Wednesday night

Cloudy with isolated flurries. 5 to 10 km/h south alpine wind. Freezing level around 1500 m.

Thursday

Cloudy with isolated flurries. 5 to 15 km/h southwest alpine wind. Treeline temperature around 0 °C with freezing level rising to 1700 m.

Friday

Mainly cloudy with isolated flurries, increasing a bit overnight. 15 to 30 km/h southwest alpine wind. Treeline temperature -2°C with freezing level around 1500 m.

Saturday

Cloudy with scattered flurries bringing less than 5 cm of new snow, including overnight amounts. 15 to 25 km/h southwest alpine wind. Treeline temperature -2 °C with freezing level to 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Wind slabs are most reactive during their formation.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.