Northwest Coastal

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

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.

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.

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.

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

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.

• 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.