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Avalanche Forecast

Archived

Jan 1st, 2025–Jan 2nd, 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 possible, human triggered probable.
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.

Adopt a cautious approach.

A problematic weak layer is surprising riders and producing large avalanches.

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

Confidence

High

Avalanche Summary

In recent days, large to very large (size 2-4) natural and human-triggered persistent slab avalanches have been reported, including several notable incidents on Tuesday. These avalanches have exhibited unexpectedly wide propagation, with some remote triggers occurring from distances of up to a kilometer away.

Notably, on the 28th this sobering near miss surprised riders, and this MIN describes skiers triggering large avalanches from valley bottom.

Snowpack Summary

The alpine has seen extensive recent wind-affect. Moderate to strong southeast winds are forecast overnight and into Thursday, and may build fresh wind slabs.

The primary layer of concern is a persistent weak layer of surface hoar and facets overlying a crust. It is buried 50 to 100 cm in the southern parts of the region, and is buried deeper, up to 200 cm, in some areas north of Stewart. This layer has been cause of several recent large avalanches with 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 current layers of concern. Treeline snow depths are around 160 cm.

Weather Summary

Wednesday night

Clear. 25 km/h east ridgetop winds. Treeline temperature -15 °C.

Thursday

Clear, with increasing cloud in the afternoon. 25 to 40 km/h southeast ridgetop wind. Treeline temperature -10 °C.

Friday

A mix of sun and cloud. 25 to 30 km/h southeast ridgetop wind. Inversion: treeline temperature -10 °C.

Saturday

Mostly sunny. 15 to 30 km/h south ridgetop wind. Inversion: Treeline temperature -10 °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.
  • Remote triggering is a concern; avoid terrain where triggering overhead slopes is possible.
  • Use conservative route selection and resist venturing into complex terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.