Wind-driven snow will form wind slabs resting on a crust, creating an excellent sliding surface.
Avoid heavily wind-loaded alpine slopes to allow time for these accumulations to stabilise, and opt for safer routes.
Wind slabs will rest directly on a crust that provides an excellent sliding surface for avalanches. Human-triggered avalanches are likely in alpine terrain. They will be found beneath ridges and alpine convexities, as well as in areas of lateral loading at the tree line. Their average thickness is estimated to be between 20 and 40 cm.
A skier could trigger small avalanches of loose, dry snow on steep slopes. The crust beneath the fresh snow provides an excellent sliding surface. Although small in size, these avalanches could carry you towards terrain features or obstacles, or cause you to slide uncontrollably on the crust.
A natural slab avalanche of size 1.5 to 2 was observed in real time by the field team in the Benny couloir, on a south-east-facing slope of the Mur des Patrouilleurs on Mont Albert. Heavy wind-driven snow accumulation had overloaded a lateral loading zone in the couloir, causing the slab to break away, which then slid down over the refrozen crust.
A slab avalanche was deliberately triggered on the Patrouilleurs wall at Mont Albert and reported to the MIN. It occurred on a south-east-facing slope subject to lateral loading. The crown thickness was 25 cm, and the length of the avalanche is estimated at 200 m.
If you head into the backcountry, thanks for sharing your observations on the Mountain Information Network (MIN).
The fresh snow will add to the 10–15 cm of snow already on the mountains, which covers a widespread crust. This crust is very hard in the alpine areas and is sometimes unable to support the weight of a skier below the tree line. Below the crust, the snowpack is well consolidated.
At mid-mountain, the average depth of the snowpack is around 140 cm.
WEATHER FOR THE CHIC-CHOCS RIDGES AND PEAKS
Additional snowfall, followed by a sharp drop in temperatures by Saturday.
Thursday evening and overnight: Snow, 4 to 7 cm. Winds turning north-westerly, 30 to 50 km/h. Low -12°C.
Friday: Intermittent snow. North-westerly wind 30–50 km/h. Dropping temperatures, high -17°C.
Saturday: A mix of sun and clouds. North-westerly wind 15–25 km/h. High -16°C.
Sunday: A mix of sun and clouds. Chance of snow showers in the afternoon. South-westerly wind of 20 to 40 km/h. High -7°C.
For more details, see the Chic-Chocs alpine weather forecast.
