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Avalanche Forecast

Archived

Mar 9th, 2023–Mar 10th, 2023

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

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

Rider triggered avalanches are possible on specific terrain features. There are a few factors to consider when evaluating snow and terrain for avalanche potential; including wind and sun exposure as well as elevation and snowpack depth.

Confidence

High

Avalanche Summary

Recent avalanche observations have been limited to solar-triggered loose dry out of steep south aspects up to size 1.5 on Wednesday.

Last week the region saw numerous natural wind slab and cornice-triggered avalanches up to size 2.

On Tuesday our field team observed a size 3 deep persistent slab avalanche near Hankin that they estimated to be around a week old. The slab propagated across the full steep, rocky feature. This has been the latest of a pattern of intermittent large deep persistent slab activity in the alpine. Observations from late February include a cornice-triggered size 2.5 at Hudson Bay and several explosive controlled size 2-3 near Ningunsaw.

Snowpack Summary

10-20 cm of recent wind affected snow sits over previously wind-hardened surfaces in the alpine. Sun crust or moist snow can be found on steep solar aspects.

Several crusts, layers of facets, or surface hoar can be found in the top 150 cm of the snowpack, but have not shown any significant avalanche activity or snowpack test results recently.

The lower snowpack consists of weak, basal facets which may become active with any rapid change or shock to the snowpack, such as heavy loading or dramatic warming.

Weather Summary

Thursday night

Clear. Light easterly wind. Alpine low -14 ˚C.

Friday

A mix of sun and cloud. Moderate southeasterly wind. Alpine high -12 ˚C.

Saturday

Mostly cloudy with isolated flurries and sunny breaks. Moderate easterly wind. Alpine high -16 ˚C.

Sunday

Mostly cloudy with isolated flurries and sunny breaks. Light easterly wind. Alpine high -14 ˚C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Conditions may have improved, but be mindful that deep instabilities are still present.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.