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Avalanche Forecast

Archived

Mar 21st, 2023–Mar 22nd, 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.

Regions

Northwest Coastal, Kitimat, Nass, Rupert, Seven Sisters, Shames, Stewart, Howson.

Hazard is improving as temperatures drop down to the valley bottom but be mindful that buried surface hoar continues to be reactive, especially in wind loaded features.

Confidence

Moderate

Avalanche Summary

On Monday, a widespread natural loose wet avalanche cycle was observed, up to 2.5, below treeline. Numerous wet loose avalanches were observed size 1-1.5 on solar aspects at alpine and treeline. Three skier triggered, size 1, windslab avalanches were reported.

On Sunday, two, natural size 3 persistent slab avalanches were observed. Both these avalanches ran to valley bottom and are suspected to have released on a weak layer of surface hoar. Two, size 1.5 persistent slab avalanches were remotely triggered by a helicopter on the same layer.

Snowpack Summary

Storm snow has settled with warm temperatures. Below 1400 m moist snow or a refrozen melt freeze crust covers the surface. The crust extends up to 2000 m on solar aspects.

A weak layer of surface hoar is found 20-50 cm down in sheltered terrain. On solar aspects, this layer appears as a melt-freeze crust. This layer continues to be reactive to skier traffic.

A second weak layer of surface hoar and/or faceted grains may be found about 60 cm deep, particularly on shaded aspects near treeline.

The remainder of the snowpack is consolidated and strong.

Weather Summary

Tuesday Night

Mainly cloudy with isolated flurries, trace accumulation. Light southwest winds at ridgetop. Treeline temperature -2°C. Freezing levels drop to 1000 m.

Wednesday

A mix of sun and cloud. Moderate southwest winds at ridgetop. Treeline temperature 0°C. Freezing levels 1100 m.

Thursday

Mainly cloudy with scattered flurries, 1-4 cm accumulation. Moderate southwest winds at ridgetop. Treeline temperature -1°C. Freezing levels 1000 m.

Friday

Partly cloudy with isolated flurries, trace accumulation. Light north winds at ridgetop. Treeline temperature -1°C. Freezing levels 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be carefull around freshly wind loaded features.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • 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.