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Avalanche Forecast

Archived

Nov 30th, 2022–Dec 1st, 2022

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

North Columbia, South Columbia, Blue River, Clearwater, Clemina, Esplanade, Jordan, North Monashee, North Selkirk, West Purcell, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, Retallack, Valhalla.

Very dangerous avalanche conditions. Travel in avalanche terrain is not recommended. Numerous reports of skier-triggered, natural, and remote trigger avalanche observations. More snow is forecast and this will add to the potential for larger avalanches to occur.

Confidence

Moderate

Avalanche Summary

Many new natural and human-triggered avalanches have been reported in the alpine and at the treeline, between 1700 and 2200 m. The common theme is that they are failing on the November 21st / surface hoar facet crust interface.

Additionally, the terrain where these avalanches occurred was steep and focused on north through to east-facing terrain. The size of these avalanches has been from size 1 (small) to size 3 (very large).

One avalanche, in particular, was remotely triggered by a skier and began as a size one and picked up enough mass to strip the snowpack to the ground resulting in a size 2.5 (large) avalanche. Temperatures are forecast to remain cool and I would surmise that this slab avalanche problem will continue to persist.

On the southern border of this region, another remote trigger avalanche was observed at 2080 m. This avalanche size 1.5 (small) failed on the Nov 21 surface hoar/ facets interface and had noted surprising propagation.

Snowpack Summary

A new snowfall Tuesday night that varies between 5 and 15 cm of new snow has been reported at numerous operations. A series of storms over the past week has delivered 30 to 50 cm of new snow. This snow fell during a period of cooling and is light and easily transported by the wind.

A layer that was buried November 21st can be found down 60 to 90 cm and is primarily a mix of surface hoar and faceted crystals. This layer is the primary concern of persistence and has been the key component of the recent natural avalanche cycle.

The average snowpack depth below the treeline is 40 to 70 cm and above that elevation is 100 to 150 cm, with wind-loaded areas presenting as 200 cm.

Weather Summary

Wednesday Night

Cloudy with snowfall, accumulation 5 to 10 cm, 20 km/h southwest wind, treeline temperature -10 to -18 °C.

Thursday

Clearing sky with some possible isolated afternoon flurries, accumulation 1 to 3 cm, 10 km/h southwest wind, treeline temperature -15 to -20 °C.

Friday

Clear sky no forecast precipitation, 20 km/h northwest wind, treeline temperature -10 to -15 °C.

Saturday

Clear sky no forecast precipitation, 20 km/h northwest wind, treeline temperature -10 to -15 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Travel in alpine terrain is not recommended.
  • Make observations and assess conditions continually as you travel.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.

Problems

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.

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.