Purcells

Weak layers in the snowpack warrant careful terrain choices and watching for signs signs of instability like cracking or whumpfing.

A size 1 deep persistent slab, 30–40 cm thick, was human-triggered below treeline on Tuesday. Last weekend, several natural and human-triggered slab avalanches (size 1 to 2) occurred near Invermere, mainly on north aspects. These avalanches failed on weak facets near the base of the snowpack.

Observations from the South Rockies are limited.

Smaller wind slab avalanches could step down to basal facets, triggering larger avalanches.

Up to 15 cm of new snow fell over the weekend. A surface hoar layer, 30 to 40 cm deep, is present on shaded slopes and atop a thin crust on sunny slopes. Near the base of the snowpack, a crust with weak sugary facets above and below caused large avalanches last weekend. Snowpack depths at treeline range from 50 to 70 cm.

Most observations are from the Invermere area, but similar conditions are likely in the South Rockies.

Thursday Night

Mostly cloudy. 10 to 30 km/h west ridgetop wind. Treeline temperature -12 °C.

Friday

Mostly cloudy with up to 1 cm of snow. 30 to 40 km/h west ridgetop wind. Treeline temperature -10 °C.

Saturday

Mix of sun and cloud. 30 km/h west ridgetop wind. Treeline temperature -8 °C.

Sunday

Mostly cloudy with up to 1 cm of snow. 30 km/h west ridgetop wind. Treeline temperature -8 °C.

More details can be found in the Mountain Weather Forecast.

• Avoid steep terrain, including convex rolls, or areas with a thin, rocky, or variable snowpack.
• Be careful with wind-loaded pockets, especially near ridge crests and rollovers.
• Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.