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Avalanche Forecast

Archived

Mar 2nd, 2023–Mar 3rd, 2023

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

South Coast Inland, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

Reactive wind slabs should be expected.

Use caution in exposed areas and avoid pockets of wind-deposited snow.

Keep in mind that if triggered, wind slabs may step down to the deep persistent slab problem resulting in large avalanches.

Confidence

Moderate

Avalanche Summary

Backcountry users reported accidentally triggering two size 1 wind slab avalanches on Wednesday.

On Monday, loose dry sluffing from steep terrain was seen as well as a remotely triggered wind slab avalanche size 1.5 that reportedly failed on facets below the recent storm snow.

A week ago, two size 3 deep persistent slab avalanches were observed just north of the Hurley summit. One was on a north-facing alpine face and the other an exposed, east-facing open slope at treeline.

Last Friday, two large (size 3-4) natural deep persistent slabs were observed on south and southeast alpine faces in the Birkenhead. We suspect these slabs occurred as a result of wind-loaded from strong northwesterly winds.

These avalanches remind us that the deep persistent slab problem remains in our region and you should make your terrain choices accordingly.

Snowpack Summary

Another 5 to 10 cm of accumulation will fall by mid-day on Friday. This will add to 35 to 50 cm of storm snow that has fallen since last weekend. In some areas, this new snow has bonded poorly to the stiff wind slabs and near-surface faceting formed by recent wind and cold temperatures.

A melt-freeze crust from late January can be found down 70 to 100 cm. At the moment this layer appears to be gaining strength though in isolated areas small facets can still be found above the crust.

There is a widespread weak layer of large sugary facets at the bottom of the snowpack. Recent avalanche activity on this layer has been confined to northern parts of the region in the Chilcotins. Snowpack depths around treeline range between 150 to 250 cm.

Weather Summary

Thursday Night

Cloudy, up to 5 cm accumulation, winds southwest 20 km/h, treeline temperatures -10 °C.

Friday

Cloudy with sunny periods, 2 cm accumulation, winds southwest 25 km/h gusting to 55, treeline temperatures -10 °C.

Saturday

A mix of sun and cloud, trace accumulation, winds northeast 15 km/h, treeline temperatures -10 to -5 °C.

Sunday

Mostly cloudy, 2 to 8 cm accumulation, winds southeast 10 to 20 km/h.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
  • Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.