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Avalanche Forecast

Archived

Jan 18th, 2024–Jan 19th, 2024

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

Regions

Blue River, Premier, Clemina, Esplanade, North Monashee, North Selkirk.

Recent persistent slab activity warrants conservative terrain selection.

New snow may form reactive storm slabs, in areas where a slab is not found dry loose avalanches are likely.

Confidence

Moderate

Avalanche Summary

On Wednesday, two persistent slab avalanches (size 1 and 2) were remotely triggered by skiers in the Northern Selkirks. These avalanches occurred on north aspects at treeline. Several natural and skier-triggered storm slabs were reported from alpine and treeline terrain up to size 2.

As snowfall continues on Friday, storm slab reactivity is expected to persist. Persistent slabs continue to be a concern and are best managed with conservative terrain choices.

Snowpack Summary

20 to 30 cm of low-density storm snow has buried a variety of snow surfaces. It sits above unconsolidated faceted snow, surface hoar and firm wind-pressed snow in open terrain at treeline and above.

Down 50 -70 cm, a crust, facet and or surface hoar layer exists. This may become a problem once the snow above starts to stiffen and form a slab.

130+ cm down another surface hoar layer exists that was buried in early December. This seems to be of most concern above 2000 m where a robust crust doesn't exist above it, or in shallow snowpack areas.

The depth of the snowpack varies greatly throughout the region and weak basal facets are present at the base of the snowpack.

Weather Summary

Thursday Night

Mainly clear, with cloud cover increasing in the early morning and no new snow. Alpine wind light from the southeast. Treeline temperature around -15 °C.

Friday

Cloudy with snowfall, up to 10 cm of accumulation. Alpine wind south 10 to 40 km/h. Treeline temperature rising to -10 °C.

Saturday

Cloudy with light snowfall, up to 5 cm of accumulation. Alpine wind south 10 to 30 km/h. Treeline temperature rising to -5 C.

Sunday

Cloudy with light snowfall, up to 5 cm of accumulation. Alpine wind south 10 to 30 km/h. Treeline temperature rising to -5 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Be carefull with sluffing in steep terrain, especially above cliffs and terrain traps.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.