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Avalanche Forecast

Archived

Dec 8th, 2024–Dec 9th, 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, East Purcell.

Buried surface hoar is increasing the reactivity of recent storm snow. Small avalanches may step down to deeper weaknesses within the snowpack.

Confidence

Moderate

Avalanche Summary

During the storm on Saturday, several natural slab avalanches were noted to size 2, mainly on north facing slopes at higher elevations. In addition, a deep persistent slab was reported on a north aspect near Invermere on depth hoar at the base of the snowpack.

Wind slab reactivity is expected to continue, while deep persistent layers remain unpredictable.

Observations are limited, please submit a MIN if you head into the backcountry!

Snowpack Summary

10-15 cm of new snow sits on various layers including sun crusts, surface hoar in sheltered areas, and wind-affected snow.

In the Invermere area, weak faceted snow at the base of the snowpack has caused several small but notable persistent slab avalanches at the base of the snowpack. It's unknown if this problem extends to the wider region, so far reports suggest it does not.

Treeline snow depths are generally 50 to 70 cm, with deeper wind-loaded pockets in the alpine.

Weather Summary

Sunday Night

Partly cloudy. 20 to 30 km/h northwest ridgetop wind. Treeline temperature -10 °C.

Monday

Sunny. 15 to 30 km/h west ridgetop wind. Treeline temperature -6 °C.

Tuesday

Sunny. 15 to 30 km/h west ridgetop wind. Treeline temperature -8 °C.

Wednesday

Sunny. 15 to 30 km/h west ridgetop wind. Treeline temperature -4 °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.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be mindful that deep instabilities are still present in the snowpack.

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.

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.