Recently formed wind slabs rest on a crust that provides an excellent sliding surface for avalanches. Avoid areas in the alpine that have recently been loaded by the wind until conditions stabilise, and opt for terrain that is safer.
Moderate to strong north-westerly winds have formed wind slabs on leeward slopes. These rest on a crust that provides an excellent sliding surface for avalanches. Human-triggered avalanches are likely in alpine terrain and possible at the tree line. They are found beneath ridges and alpine convexities, as well as in lateral loading zones at the tree line. Their average thickness is 20 to 40 cm.
On Thursday march 26th, 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.
Thursday, 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 wind caused significant spatial variability in alpine and at the tree line, with conditions ranging from icy surfaces to powder snow, including packed snow and soft wind slabs.
Between 10 and 20 cm of light, low density snow covers a widespread crust. This crust is very hard in the alpine. Below the tree line, it is sometimes more brittle and unable to support a skier’s weight. Under 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
A high-pressure system will bring clearer skies and cold temperatures on Saturday.
Friday evening and night: Partly cloudy, light snow. North-westerly wind 30–50 km/h. Low -23°C.
Saturday: A mix of sun and clouds. Westerly wind 20–40 km/h. High -14°C.
Sunday: Cloudy. Chance of snow showers, 2 to 4 cm. South-westerly wind 20 to 40 km/h. Maximum -7°C.
Monday: Snow 5 to 10 cm, chance of rain or freezing rain. Southerly wind 20 to 40 km/h. Maximum +1°C. Freezing level at 400m.
For more details, see the Chic-Chocs alpine weather forecast.
