Avalanche Forecast

Archived

Dec 10th, 2024–Dec 11th, 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.

Below Treeline

Natural avalanches unlikely.

Regions

Purcells, East Purcell.

While avalanches are expected to be small, slabs may step down to deeper weaknesses within the snowpack.

Surface hoar may still be triggerable below the recent snow

Confidence

Moderate

Avalanche Summary

On Monday a natural wind slab was observed from north facing alpine terrain, and dry loose sluffing was observed in wind sheltered areas.

Deep persistent slabs have been reported within the last 3 days, to size 1.5 from explosive and human triggers, on north facing slopes at treeline and below.

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 wind affected snow sits on sun crusts on south facing slopes, surface hoar in sheltered areas, and previously wind-affected snow.

In the Invermere area, weak faceted snow at the base of the snowpack has caused several small persistent slab avalanches at the base of the snowpack. So far reports suggest it does not extend throughout the forecast region.

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

Weather Summary

Tuesday Night

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

Wednesday

Partly cloudy with a chance of flurries. 10 to 20 km/h west ridgetop wind. Treeline temperature -6 °C.

Thursday

Mostly clear skies. 10 to 20 km/h southwest ridgetop wind. Treeline temperature -6 °C.

Friday

Mostly clear skies. 10 to 20 km/h southwest ridgetop wind. Treeline temperature -6 °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.
Approach steep and open slopes at and below treeline cautiously, as buried surface hoar may exist.
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.