Northwest Coastal

A problematic weak layer has surprised riders and triggered large avalanches. Conservative terrain selection is your best defence against buried weak layers.

On Friday, explosives triggered several small size 1-1.5 wind slab avalanches, with crowns 20-40 cm deep.

Thursday and Friday, natural and rider-triggered wind slab avalanches to size 2 were reported.

A persistent weak layer has recently produced very large natural and human-triggered avalanches, including remote-triggering up to 1 km away. On the 28th this near miss surprised riders, and this MIN describes avalanches triggered from valley bottom.

5 to 15 cm of fresh snow covered older wind affected snow. Easterly winds have reverse loaded-features, and wind slabs can be found on various aspects. Soft snow still exists in sheltered terrain and in the trees.

Our primary concern is a persistent weak layer of surface hoar and facets overlying a crust. It is buried 50 to 100 cm deep in the southern parts of the region and up to 200 cm deep in areas north of Stewart. Several recent large avalanches have failed on this layer producing wide propagation.

The lower snowpack is well settled, with no deeper layers of concern. Treeline snow depths are around 160 cm.

Saturday night

Cloudy with isolated flurries, trace to 10 cm of snow. 20 to 30 km/h south ridgetop wind. Treeline temperature -14 °C.

Sunday

Mostly cloudy. 25 to 40 km/h west ridgetop wind. Treeline temperature -6 °C.

Monday

Sunny. 30 to 70 km/h southwest ridgetop wind. Treeline temperature -4 °C.

Tuesday

Cloudy with flurries, up to 10 cm. 40 to 80 km/h southwest ridgetop wind. Treeline temperature -2 °C.

More details can be found in the Mountain Weather Forecast.

• Be aware of the potential for large avalanches due to buried weak layers.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
• In times of uncertainty, conservative terrain choices are our best defense.