Avalanche Forecast

Archived

Jan 5th, 2023–Jan 6th, 2023

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 unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Northwest Inland, Kispiox, Microwave-Sinclair, South Bulkley, South Bulkley, Telkwa.

Careful terrain choices are needed to manage uncertainty about buried weak layers and the ongoing impact of strong wind.

Confidence

Moderate

Avalanche Summary

Preliminary reports from Thursday include a large (size 2) wind slab avalanche that occurred on a southwest slope at treeline during a period of strong wind from the northeast.

Over the weekend and last week, there were several reports of larger (up to size 2.5) natural avalanches at all elevations releasing on a 30 to 60 cm deep facet layer. Triggering an avalanche on this weak layer is still possible under the current conditions.

Snowpack Summary

Strong to extreme wind is forming drifts and wind slabs in alpine terrain and along ridges, while sheltered terrain has 10 to 15 cm of low density snow. This snow may sit above a layer of small surface hoar that will sluff easily in steep terrain. A weak layer of facets that formed during the arctic outbreak in December is buried 30 to 60 cm deep. Recent avalanche activity and snowpack tests suggest human-triggering is possible for this layer. We are uncertain about the layer's spatial distribution, but observations suggest it is fairly widespread.

Weather Summary

Thursday night

Mostly cloudy, isolated flurries with up to 3 cm of snow, 40 to 50 km/h wind from the southeast, treeline temperatures around -10 °C.

Friday

Cloudy with afternoon flurries brining up to 5 cm of snow, 40 to 60 km/h wind from the southwest, treeline temperatures warm to -5 °C.

Saturday

Mix of sun and cloud, no precipitation, 30 to 50 km/h wind from the south, treeline temperatures around -5 °C.

Sunday

Mix of sun and cloud, no precipitation, 30 to 50 km/h wind from the southeast, treeline temperatures around -8 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Use conservative route selection and resist venturing out into complex terrain.
Avoid freshly wind loaded terrain features.
Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.
Avoid making assumptions about this layer based on the presence of aggressive tracks on adjacent slopes

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.