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Avalanche Forecast

Archived

Dec 17th, 2023–Dec 18th, 2023

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

Regions

Kitimat, Nass, Rupert, Seven Sisters, Shames, Howson.

New wind slabs continue to bury weak layers, creating a complex avalanche hazard. Monitor for signs of instability and stick to low-consequence terrain.

Confidence

Moderate

Avalanche Summary

A size 1.5 storm slab avalanche was triggered by a skier on Thursday near Terrace. This avalanche failed on buried surface hoar, 30 cm deep from a feature near ridge crest.

On Wednesday, a large avalanche cycle occurred. Natural and explosive triggered avalanches avalanches, up to size 3, were reported throughout the region. These avalanches mostly occurred on lee slopes or lee features. One of these avalanches was reported to have failed on buried surface hoar, 50 cm deep.

Snowpack Summary

New snow amounts of 15 cm on Sunday has been redistributed by southwest winds. This will be added to the 20 to 45 cm of snow that fell earlier in the week which was also accompanied by strong south and southwesterly winds.

A buried layer of weak, feathery surface hoar crystals can now be found 25 to 50 cm deep. While another layer of buried surface hoar may exist deeper in the snowpack, roughly 55 to 95 cm below the surface.

The remaining mid and lower snowpack contains several crusts from early in the season that are generally well-bonded to the surrounding snowpack.

Currently, the height of snow is highly variable and decreases significantly at lower elevations.

Weather Summary

Sunday Night

Cloudy, 5 to 10 cm accumulation, ridgetop winds southwest 30 km/h, treeline temperature -5 °C. 

Monday

Cloudy, 5 to 10 cm accumulation, ridgetop winds southwest 30 to 50 km/h, treeline temperature -2 °C.

Tuesday

Cloudy with late day clearing, 10 to 15 cm accumulation, ridgetop winds southerly 30 to 40 km/h, treeline temperature -3 °C.

Wednesday

Cloudy, 5 cm accumulation, ridgetop winds southerly 70 km/h, treeline temperatures -3 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid areas where the snow feels stiff and/or slabby.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Watch for fresh storm slabs building throughout the day.

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.