Avalanche Forecast

Archived

Mar 15th, 2025–Mar 16th, 2025

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Purcells, East Purcell, St. Mary.

Fresh wind slabs will be building on Sunday.

Wind slabs could step down to a deeper persistent weak layer triggering a much larger avalanche.

Confidence

Moderate

Avalanche Summary

Fri: Several large to very large (size 2-3) persistent slab avalanches occurred in the region. All of them initiated in the alpine.

Thurs: A large (size 2) naturally-triggered persistent slab near Invermere and a size 2.5 persistent slab near Kimberley were observed.

Tues: Avalanche control produced large avalanches (up to size 3.5) in the central-western part of the region.

Looking forward: Wind slabs and persistent slabs are expected to remain triggerable on Sunday.

Snowpack Summary

15 - 30 cm of snow accumulated over the last few days forming wind slabs at upper elevations. An additional 5 - 10 cm of new snow combined with strong southwest winds is forecast to fall overnight and through Sunday. This is expected to create fresh wind slabs on wind-loaded north and east facing slopes near ridgetops.

Combined, the recent snow covers a crust on sunny slopes and lower elevations, and surface hoar or facets on sheltered and shady upper elevations. Several weak layers consisting of a crust, facets or surface hoar from February and January remain a concern, buried 30 to 60 cm. A layer of facets from early December is buried 70 to 120 cm. In many areas, facets or depth hoar make up the base of the snowpack.

Weather Summary

Saturday Night

Mostly cloudy with 1 to 5 cm of snow. 10 to 25 to 40 km/h southwest ridgetop winds. Treeline temperature -9 °C.

Sunday

Mostly cloudy, with 2 to 5 cm of snow. 20 to 30 km/h south ridgetop winds. Treeline temperature -5 °C.

Monday

A mix of sun and clouds. 15 to 30 km/h west ridgetop winds. Treeline temperature -5 °C.

Tuesday

A mix of sun and cloud. 10 to 25 km/h west ridgetop winds. Treeline temperature -7 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Be aware of the potential for large, destructive avalanches due to deeply buried weak layers.
Avoid steep, rocky, and wind-affected areas where triggering slabs is more likely.
Be careful with wind-loaded pockets, especially near ridge crests and rollovers.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.