Avalanche Forecast

Archived

Dec 27th, 2024–Dec 28th, 2024

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Kootenay Boundary, Bonnington, Grohman, Kootenay Pass, Norns, Rossland, Ymir.

There's no doubt that new snow and wind will form fresh, reactive storm slabs. Uncertainty lies deeper in the snowpack where dangerous weak layers may be at play.

Confidence

Moderate

Avalanche Summary

On Thursday, skiers near Rossland remote-triggered storm slabs (size 1-2) on north-facing treeline and below treeline terrain. Natural storm slabs up to size 2 were also observed in the area. Explosive control near Nelson produced storm slabs up to size 2 on a variety of aspects at treeline.

No new persistent slab activity has been reported since the storm, but observations remain limited.

Snowpack Summary

Continued snowfall adds to 15 to 40 cm of recent new snow. Accompanying southwest wind will redistribute this new snow, forming deeper deposits on leeward slopes at higher elevations.

A crust is present near the surface at lower elevations.

The upper snowpack continues to settle and bond well following significant snowfall over the last two weeks.

Weak layers of surface hoar or facets and a crust may persist in the mid-snowpack, and snowpack tests continue to indicate potential instability.

The lower snowpack is generally strong and well-bonded.

Weather Summary

Friday Night

Cloudy with 5 to 10 cm of new snow. 10 to 30 km/h southwest ridgetop wind. Treeline temperature -6 °C.

Saturday

Cloudy with 5 to 15 cm of new snow. 15 to 40 km/h southwest ridgetop wind. Treeline temperature -5 °C.

Sunday

Cloudy with up to 5 cm of new snow. 5 to 15 km/h northeast ridgetop wind. Treeline temperature -5 °C.

Monday

A mix of sun and cloud with isolated flurries. 10 to 30 km/h west ridgetop wind. Treeline temperature -7 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

In times of uncertainty, conservative terrain choices are our best defense.
Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Surface hoar distribution is highly variable. Avoid generalizing your observations.

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.