Avalanche Forecast

Archived

Jan 8th, 2025–Jan 9th, 2025

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

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.

Regions

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

New snow and wind are creating very dangerous avalanche conditions. Travel in avalanche terrain is not recommended.

Confidence

Moderate

Avalanche Summary

Observations have been limited by poor visibility during the storm. On Tuesday, natural storm slabs were observed up to size 3 in the alpine and size 2 below treeline. We expect similar natural avalanche activity to be ongoing through the storm on Thursday.

On Monday, north of Stewart, a vehicle triggered a size 1.5 persistent slab avalanche on a northwest aspect in the alpine.

Snowpack Summary

Another 15-30 cm of snow is expected by the end of the day Thursday, bringing storm totals to 30 to 70 cm. The new snow arrives with strong to extreme winds, particularly near Terrace, so significant wind transport is expected at upper elevations. Below 1200 m, the snow surface may be moist, wet or crusty.

The recent snow isn't expected to bond well where it sits on a layer of buried surface hoar, facets, or a thin crust.

A weak layer of surface hoar and facets overlying a crust is buried 60 to 120 cm deep in the southern parts of the region, and up to 200 cm deep in areas north of Stewart. If the new snow overloads this layer, causing it to fail, the resulting avalanches will be very large and destructive.

Weather Summary

Wednesday night

Cloudy with around 5 cm of snow. Southwest ridgetop wind increasing 20 to 50 km/h. Treeline temperature -2°C. Freezing level 1200 m near Terrace, 800 m near Stewart.

Thursday

Cloudy with 15 to 30 cm of snow. 70 to 100 km/h southwest ridgetop wind. Treeline temperature -1 °C. Freezing level 1200 m near Terrace, 800 m near Stewart.

Friday

Cloudy with 10 to 20 cm of snow. 50 to 70 km/h southwest ridgetop wind. Treeline temperature -2 °C. Freezing level 800 to 1000 m.

Saturday

Cloudy. 30 to 40 km/h northwest ridgetop wind. Treeline temperature -5 °C. Freezing level valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid avalanche terrain during periods of heavy loading from new snow, wind, or rain.
Be aware of the potential for large avalanches due to buried weak layers.
Avoid exposure to overhead avalanche terrain; avalanches may run surprisingly far.
Conservative terrain selection is critical; choose gentle, low consequence lines.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.