Avalanche Forecast

Archived

Jan 9th, 2023–Jan 10th, 2023

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal, Northwest Inland, Stewart, Kispiox, Ningunsaw, Ningunsaw.

Concerns for wind slabs in steep terrain and buried weak layers warrant careful terrain choices.

Confidence

Moderate

Avalanche Summary

A very large (size 3) persistent slab avalanche was remotely triggered on Sunday. This avalanche failed on a 50 cm deep facet layer and released on a northeast aspect at 1900 m. We continue to get evidence that this persistent slab can be easily triggered by riders in specific areas.

Otherwise, there were several reports of smaller (size 1 to 2) wind slab avalanches over the weekend, primarily occurring on north-facing aspects.

Snowpack Summary

Recent strong southerly wind formed wind slabs in lee terrain features near ridges. Several persistent weak layers may be found in the top meter of the snowpack. These include a surface hoar layer buried on Dec 28 found 40 to 60 cm deep and a facet layer buried on Dec 23 found 60 to 100 cm deep. In alpine terrain, triggering one of these layers is most likely on steep rocky slopes where they present as facets. In treeline terrain, the layers are most likely triggered on steep slopes in open trees where they present as preserved surface hoar.

Weather Summary

Monday night

Partly cloudy, no precipitation, 20 to 30 km/h southeast wind, treeline temperatures drop to -12 °C.

Tuesday

Cloudy with isolated flurries and trace accumulations of snow, 20 to 30 km/h southeast wind, treeline temperature -8 °C.

Wednesday

Mostly cloudy with isolated flurries and trace accumulations of snow, 20 to 30 km/h south wind, treeline temperature -6 °C.

Thursday

Mostly cloudy with isolated flurries and trace accumulations of snow, 40 to 50 km/h south wind, treeline temperature -8 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Be especially cautious as you transition into wind affected terrain.
Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
Use conservative route selection and resist venturing out into complex terrain.
Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.