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Avalanche Forecast

Archived

Mar 3rd, 2023–Mar 4th, 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.

Southerly winds have redistributed recent storm snow.

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

In the last couple of days, there have been numerous reports of storm slab, wind slab, and loose dry avalanches most of these were released naturally and a few were human-triggered. They ranged in size between one and two. Expect to see more of these avalanches if you venture into the back country.

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

Our region saw 30 to 50 cm of storm snow this past week. Southerly winds have begun to redistribute this new snow into reactive wind slabs. New snow and wind slabs sit on a variety of surfaces. 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.

The mid-snowpack is well consolidated. This is not the case for the lower snowpack. 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 200 and 250 cm.

Weather Summary

Friday Night

Partly cloudy, trace accumulation, winds south 10 to 15 km/h, treeline temperatures -10 °C.

Saturday

Mostly sunny, no accumulation, winds east southeast 10 to 20 km/h, treeline temperatures -10 to -7 °C.

Sunday

A mix of sun and cloud, 5 to 8 cm accumulation, winds east 10 to 20 km/h treeline temperatures -8 °C.

Monday

A mix of sun and cloud, no accumulation, winds southwest 10 km/h, treeline temperatures -10 to -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be especially cautious as you transition into wind affected terrain.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Keep your guard up at lower elevations. Wind slab formation has been extensive.
  • 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.