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Avalanche Forecast

Archived

Dec 5th, 2024–Dec 6th, 2024

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
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, East Purcell.

Wind slabs may be reactive in leeward terrain features in the alpine.

Concern remains for a weak layer near the base of the snowpack in shallow areas with facets over a crust.

Confidence

Low

Avalanche Summary

On Tuesday, a small (size 1.5) natural deep persistent avalanche occurred near Invermere. It was on a northeast aspect in the alpine.

Snowpack Summary

Treeline snow depths are generally 50 to 70 cm, with deeper wind-loaded pockets in the alpine. New surface hoar is growing on the surface in sheltered terrain. Wind-affected surfaces are expected in exposed terrain at higher elevations. A new sun crust is likely forming on steep, sun-exposed slopes.

In the Invermere area, weak faceted snow at the base of the snowpack has caused several small but notable deep persistent slab avalanches.

Early-season hazards are present at all elevations. Stay alert and assess terrain carefully.

Weather Summary

Thursday Night

Mostly clear. 10 to 20 km/h southwest ridgetop wind. Treeline temperature -5 °C.

Friday

A mix of sun and cloud. 20 km/h southwest ridgetop wind. Treeline temperature -3 °C.

Saturday

Cloudy with up to 15 cm of snow. 30 to 50 km/h southwest ridgetop wind. Treeline temperature -3 °C.

Sunday

A mix of sun and cloud with up to 2 cm of snow. 20 to 30 km/h northwest ridgetop wind. Treeline temperature -7 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind-loaded pockets, especially near ridge crests and rollovers.
  • Be mindful that deep instabilities are still present in the snowpack.
  • Triggering deep layers is more likely if the snow surface didn't freeze overnight.

Problems

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

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.