Avalanche Forecast

Archived

Dec 27th, 2024–Dec 28th, 2024

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Purcells, Crawford, Dogtooth, East Purcell, Moyie, St. Mary, West Purcell.

Rocky, wind-affected areas are a prime suspect for large, human-triggered avalanches.

Seek out sheltered, moderate-angled slopes for the best and safest riding.

Confidence

Moderate

Avalanche Summary

Last Tuesday, a large skier-triggered avalanche (see this MIN) occurred in the Kicking Horse backcountry.

On Thursday, storm slabs were reactive to skier traffic (size 1) in alpine and treeline terrain near Golden. Explosive control in the area produced a size 2 persistent slab from north-facing alpine terrain.

A natural (size 2) storm slab was observed near Kaslo from a southwest aspect at treeline on Thursday.

Snowpack Summary

Continued snowfall adds to 5 to 25 cm of recent new snow. Accompanying southwest wind will redistribute this new snow, forming deeper deposits on leeward slopes at higher elevations.

A layer buried in early December is found roughly 20 to 90 cm below the surface. This layer varies, consisting of weak surface hoar or facetted crystals on shaded slopes and a sun crust with facets on south-facing slopes.

The base of the snowpack is made up of a thick crust and facets in many areas.

Weather Summary

Friday Night

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

Saturday

Cloudy with 1 to 10 cm of new snow. 10 to 40 km/h southwest ridgetop wind. Treeline temperature -7 °C.

Sunday

Mostly cloudy with up to 5 cm of new snow. 5 to 15 km/h northeast ridgetop wind. Treeline temperature -8 °C.

Monday

A mix of sun and cloud with isolated flurries. 10 to 30 km/h west ridgetop wind. Treeline temperature -8 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid freshly wind-loaded features, especially near ridge crests, rollovers, and in steep terrain.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avoid shallow snowpack areas, rocky outcrops, and steep terrain where triggering is most likely.

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.