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Avalanche Forecast

Archived

Jan 7th, 2023–Jan 8th, 2023

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

Regions

Northwest Inland, Kispiox, Microwave-Sinclair, Ningunsaw, South Bulkley, South Bulkley, Telkwa.

Take a cautious approach to wind-loaded areas as recently formed wind slabs may remain reactive to human triggering.

Concern for buried weak layers warrants conservative terrain choices and avoidance of steep and convex slopes.

Confidence

Moderate

Avalanche Summary

On Friday, a small (size 1.5) natural wind slab was observed on a northwest aspect in the alpine in the north of the region.

On Thursday, as northeasterly winds increased, a natural size 2 wind slab was observed. This avalanche occurred as a result of rapid snow loading from wind transport. The avalanche failed on a weak layer of surface hoar, which contributed to the wide propagation of the avalanche. See full report here.

Over the last week, there were several reports of larger (up to size 2.5) natural avalanches at all elevations releasing on a 30 to 60 cm deep facet layer. Triggering an avalanche on this weak layer is still possible under the current conditions.

Snowpack Summary

Recent strong to extreme winds have formed drifts, wind-scoured areas, and wind slabs in alpine terrain and along ridges. Sheltered terrain has 10 to 15 cm of low-density snow. This snow may sit above a layer of small surface hoar that will sluff easily in steep terrain. A weak layer of facets that formed during the arctic outbreak in December is buried 30 to 60 cm deep. Recent avalanche activity and snowpack tests suggest human triggering is possible for this layer. We are uncertain about the layer's spatial distribution, but observations suggest it is fairly widespread.

Weather Summary

Saturday night

Clear periods. Alpine temperatures drop to a low of -4 °C. Ridge wind southeast 10-30 km/h. Freezing level at valley bottom.

Sunday

Cloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -4 °C. Ridge wind southeast 15-25 km/h. Freezing level rises to 400 metres.

Monday

Cloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -6 °C. Ridge wind southeast 15-25 km/h. Freezing level rises to 400 metres.

Tuesday

Mainly cloudy with isolated flurries. Alpine temperatures reach a high of -6 °C. Ridge wind southeast 20 km/h. Freezing level at valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Use conservative route selection and resist venturing out into complex terrain.
  • Avoid freshly wind loaded terrain features.
  • Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.

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.