Avalanche Forecast

Archived

Mar 9th, 2025–Mar 10th, 2025

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

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.

Regions

Purcells, East Purcell, St. Mary, Bull.

New snow lands on a variety of surfaces, assess bond of new snow as you change aspect and elevation.

Take extra caution when transitioning into wind affected terrain.

Confidence

Moderate

Avalanche Summary

Friday: Cornice falls were reported to have triggered large avalanches, mostly contained within the surface snow.

Thurs: One person was buried in an avalanche in Pedley Pass, just east of the forecast area. See details about that avalanche and a few nearby in these MINs.

Wed: Numerous, small natural and human triggered dry loose avalanches were reported in steep terrain, as well as a few small rider and explosive triggered slab avalanches.

Snowpack Summary

The upper snowpack is currently quite variable. New snow falls on a sun crust on solar aspects, and surface hoar or facets in sheltered areas or north aspects. The new snow is being wind redistributed by moderate southwest winds into fresh wind slabs.

A few 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 exist at the base of the snowpack. These deeper layers are not currently creating an avalanche problem.

Weather Summary

Sunday Night

Mainly cloudy, with up to 12 cm snow. 15 to 25 km/h southwest ridgetop wind. Freezing level falling to 1400 m.

Monday

A mix of sun and cloud, with a possibility of isolated flurries. 10 to 20 km/h west ridgetop winds. Treeline temperature -6 °C.

Tuesday

A mix of sun and cloud, with isolated flurries, up to 2 cm. 10 to 20 km/h southwest ridgetop winds. Treeline temperature -1 °C.

Wednesday

A mix of sun and cloud, with isolated flurries. 10 to 20 km/h southwest ridgetop winds. Treeline temperature -1 °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.
Pay attention to the wind; once it starts to blow, sensitive wind slabs are likely to form.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.