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Avalanche Forecast

Archived

Jan 2nd, 2023–Jan 3rd, 2023

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

Sea To Sky, Brandywine, Garibaldi, Homathko, Powell River, Spearhead, Tantalus, Sasquatch, Sky Pilot.

A widespread crust has been buried by wind slabs at higher elevations and consolidated recent snow in sheltered areas.

A deep persistent slab problem may not seem evident or reactive but can produce very large and destructive avalanches.

Choose terrain carefully as you travel.

Confidence

Moderate

Avalanche Summary

On Sunday, wind slab avalanche activity was reported to have occurred naturally and accidentally by skiers. These were size 1 to 2.

On Friday and Saturday, numerous natural and human-triggered storm and wind slabs were reported up to size 2. These slabs mainly occurred in wind-loaded terrain and primarily failed on the underlying rain crust.

Several large (size 2 to 2.5) deep persistent slab avalanches were produced during explosive control work last Thursday. All in alpine terrain on a variety of aspects with crowns of 1.5 to 2 m deep. This layer now presents a low-probability but high-consequence problem that is atypical for our coastal snowpack. Learn more about the nature of this deep persistent slab problem from this forecaster blog.

Looking forward, wind slabs may remain reactive to human triggering for longer than is typical due to the slick crust they are sitting on. Avoid wind-loaded terrain and watch for signs of instability as you travel.

Snowpack Summary

Strong southwest winds, creating hard wind-affected surfaces in open areas and wind slabs in lee terrain features from the 30 to 60 cm that accumulated by the end of last week. New wind slabs and recent snow have covered a rain crust that formed on December 26th. This crust is thin and breakable at higher elevations and up 10 cm thick at lower elevations.

The mid-snowpack consists of moist snow below the crust at lower elevations. At higher elevations, a series of crusts and denser snow can be found below this December 26th rain crust.

Near the base of the snowpack, a weak facet/crust layer can be found.

Total snow depths are roughly 100 to 200 cm at treeline.

Weather Summary

Monday Night

Cloudy with clear periods, no accumulation, winds south 15 to 30 km/h, temperatures -5 to 0 °C at 1500 m.

Tuesday

Mostly cloudy, up to 6 cm accumulation, winds south to southeast 20 km/h, temperatures -8 to -5 °C at 1500 m.

Wednesday

A mix of sun and cloud, trace accumulation, winds southeast to east 20 km/h, temperatures -5 °C at 1500 m.

Thursday

Cloudy, up to 10 cm accumulation, winds southeast 20 km/h, freezing level reaching 1600 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Keep in mind the crust offers an excellent bed surface for avalanches.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.

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.