Avalanche Forecast

Archived

Jan 3rd, 2025–Jan 4th, 2025

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, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

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

A problematic weak layer has surprised riders and triggered large avalanches.

Remote triggering is a concern, avoid exposure to steep overhead slopes.

Confidence

High

Avalanche Summary

Natural and rider-triggered wind slab avalanches to size 2 were reported over the past couple of days.

In the last week, very large (size 2-4) natural and human-triggered persistent slab avalanches have been reported. These avalanches have exhibited unexpectedly wide propagation, with some remote triggers occurring from distances up to one kilometre away.

On the 28th this near miss surprised riders, and this MIN describes avalanches triggered from valley bottom.

Snowpack Summary

The alpine has seen extensive recent wind affect. Recent strong winds have varied in direction, building slabs on many 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. Looking forward, we expect this layer to remain a concern for many days, or even weeks.

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

Weather Summary

Friday night

Cloudy. 10 to 20 km/h southwest ridgetop wind. Treeline temperature -14 °C.

Saturday

Cloudy with isolated flurries, trace to 10 cm snow. 25 to 45 km/h west ridgetop wind. Treeline temperature -12 °C.

Sunday

Mostly cloudy. 20 to 40 km/h southwest ridgetop wind. Treeline temperature -10 °C.

Monday

Sunny. 20 to 40 km/h west ridgetop wind. Treeline temperature -8 °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

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.

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.