Avalanche Forecast

Archived

Jan 6th, 2025–Jan 7th, 2025

Alpine

Natural and human triggered avalanches likely.

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 and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

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

If you see less than 15 cm of new snow, hazard may only be considerable.

Avoid avalanche terrain and overhead hazard during periods of heavy loading from new snow and wind.

Confidence

Moderate

Avalanche Summary

On Monday, north of Stewart, a vehicle triggered a size 1.5 slab on the persistent weak layer. It failed on a northwest slope in the alpine.

Thursday and Friday, natural, human, and explosive-triggered wind slab avalanches, (size 1 to 2) were reported.

Looking forward, we expect the likelihood of both natural and human-triggered avalanches to significantly increase during this stormy period.

Snowpack Summary

5 to 15 cm of recent snow is covering surface hoar and facets or a thin crust in some areas. An additional 10 to 25 cm accompanied by extreme southerly ridgetop winds is forecast overnight and throughout Tuesday. This combo is expected to build fresh storm slabs and deep wind-deposits on leeward slopes.Soft snow still exists in sheltered terrain and in the trees.

An additional concern is a persistent weak layer of surface hoar and facets overlying a crust. It 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. Several large avalanches failed on this layer in the last big storm, producing wide propagation.

Treeline snow depths are around 160 cm.

Weather Summary

Monday night

Mostly cloudy with 0 to 5 cm of snow. 80 to 100 km/h south ridgetop wind. Treeline temperature -4 °C.

Tuesday

Cloudy with 10 to 30 cm of snow, or possible rain below 1500 m. 80 to 100 km/h south ridgetop wind. Treeline temperature 0 °C. Freezing level rising to 1500 m near Terrace.

Wednesday

Overnight snow 10 to 20 cm by morning. Cloudy, 25 to 35 km/h west ridgetop wind. Treeline temperature -1°C.

Thursday

Cloudy with 15 to 30 cm of snow. 80 to 100 km/h west ridgetop wind. Treeline temperature 0 °C. Freezing level rising to 1600 m near Terrace.

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.
Storm slab size and sensitivity to triggering will likely increase through the day.
Be aware of the potential for large avalanches due to buried weak layers.

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.