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Avalanche Forecast

Archived

Dec 23rd, 2024–Dec 24th, 2024

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.
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.

Carefully assess steep slopes, as small surface avalanches could trigger deeper weak layers.

Confidence

Moderate

Avalanche Summary

Numerous avalanches were reported over the weekend, with a common theme across the region being wind slabs up to size 2, triggered by natural causes, skiers, and explosives. They primarily occurred in steep, alpine terrain on a variety of aspects, with depths up to 60 cm.

One explosive-triggered size 2.5 avalanche was reported in the north of the region. It failed on a buried weak layer, producing a crown up to 100 cm deep. This occurred in very steep, rocky, alpine terrain.

Snowpack Summary

20 to 40 cm of recent snow continues to settle and bond to underlying surfaces. Recent southwest winds have redistributed this snow into deeper deposits 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. The only location where this basal layer has shown signs of instability is in the Invermere area.

Weather Summary

Monday Night

Partly cloudy. 10 to 30 km/h southwest ridgetop wind. Treeline temperature -5 °C.

Tuesday

Partly cloudy with 2 to 8 cm of snow. 20 to 40 km/h southwest ridgetop wind. Treeline temperature -5 °C.

Wednesday

Mix of sun and cloud with 0 to 2 cm of snow. 10 to 30 km/h southwest ridgetop wind. Treeline temperature -7 °C.

Thursday

Mostly cloudy with 0 to 2 cm of snow. 10 to 30 km/h southwest ridgetop wind. Treeline temperature -7 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful as you transition into wind-affected terrain.
  • Avoid steep, rocky, and wind-affected areas where triggering slabs is more likely.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.