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Avalanche Forecast

Archived

Jan 1st, 2023–Jan 2nd, 2023

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.
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.

Avoid wind-loaded areas at upper elevations. Recently formed wind slabs overlie a slick crust in some areas and could remain reactive to human triggering for longer than is typical.

A low-probability but high-consequence deep persistent slab problem should have you avoiding thin rocky areas and exposure to overhead hazards. Learn more about how to manage this problem in the avalanche summary...

Confidence

Moderate

Avalanche Summary

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.

Please continue to post your observations and photos to the Mountain Information Network.

Snowpack Summary

Last week, 30-60 cm of storm snow was accompanied by strong southwest winds, creating hard wind-affected surfaces in open areas and wind slabs in lee terrain features. This new snow overlies a rain crust formed earlier in the week. 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 a crust at lower elevations and a series of crusts and denser snow at upper elevations.

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

Sunday night

Mainly cloudy. Alpine temperatures drop to a low of -5 °C. Ridge wind south 15-25 km/h. Freezing level at valley bottom.

Monday

Cloudy with sunny periods. Alpine temperatures reach a high of -1 °C. Ridge wind south 15 km/h gusting to 40 km/h. Freezing level rises to 1400 metres.

Tuesday

Cloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -5 °C. Ridge wind southwest 10-25 km/h. Freezing level rises to 800 metres.

Wednesday

Cloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -2 °C. Ridge wind southeast 15-30 km/h. Freezing level rises to 1200 metres.

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.