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Avalanche Forecast

Archived

Jan 5th, 2025–Jan 6th, 2025

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

Regions

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

Winds are expected to increase. If you see blowing snow, expect to find fresh wind slabs.

Sticking to conservative terrain selection is your best defence against buried weak layers.

Confidence

Moderate

Avalanche Summary

On Friday, explosives triggered several small size 1-1.5 wind slab avalanches, with crowns 20-40 cm deep.

Thursday and Friday, natural and rider-triggered wind slab avalanches to size 2 were reported.

A persistent weak layer recently produced very large natural and human-triggered avalanches, including remote-triggering up to 1 km away. On Dec 28th this near miss surprised riders, and this MIN describes avalanches triggered from valley bottom.

Snowpack Summary

5 to 15 cm of recent snow covers older wind-affected snow. Easterly winds have reverse-loaded features and wind slabs can be found on various aspects. Soft snow still exists in sheltered terrain and in the trees.

Our primary concern is a persistent weak layer of surface hoar and facets overlying a crust. It is buried 50 to 100 cm deep in the southern parts of the region and up to 200 cm deep in areas north of Stewart. Several recent large avalanches have failed on this layer producing wide propagation.

The lower snowpack is well settled, with no deeper layers of concern. Treeline snow depths are around 160 cm.

Weather Summary

Sunday night

Mostly cloudy. 20 to 30 km/h west ridgetop wind. Treeline temperature -5 °C.

Monday

Sunny. 30 to 70 km/h southwest ridgetop wind. Treeline temperature -4 °C.

Tuesday

Cloudy with flurries, up to 20 cm. 40 to 80 km/h southwest ridgetop wind. Treeline temperature -3 °C.

Wednesday

Overnight flurries, 15 to 40 cm snow by morning. 15 to 30 km/h southwest ridgetop wind. Treeline temperature -6°C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for large avalanches due to buried weak layers.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • In times of uncertainty, conservative terrain choices are our best defense.

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.