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Avalanche Forecast

Archived

Mar 5th, 2023–Mar 6th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
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, human triggered possible.
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 can be found on all aspects and all elevations throughout our region.

There were two avalanche incidents on Saturday in the Duffey area. More information can be found in the MIN.

Keep in mind that if triggered, wind slabs may step down to the deep persistent slab problem resulting in large avalanches, especially in shallow snowpack areas in the north and east of the region.

Confidence

Moderate

Avalanche Summary

On Saturday, two avalanche incidents occurred in the Duffey area, both on south aspects between 1650 and 1770 m elevation. We have received reports of touchy wind slabs, likely related to a period of outflow winds from the northeast causing reverse loading. Wind slabs should be expected on all aspects and at all elevations throughout our region. Wind slabs may be more reactive and persist for longer than what is normal due to them potentially sitting on a crust. Reports of these are posted on the MIN page.

In most areas of our region, more natural wind slab avalanches were reported. They reached up to size 2.5. Their elevation was in the alpine and as far down as below treeline. The aspect that they occurred on ranged around the compass.

The deep persistent slab problem remains in our region, especially in the northwestern zones. When making terrain choices, please keep this issue at the forefront of your thought process.

Snowpack Summary

A variety of winds have begun to redistribute the 30 to 50 cm that fell last week, creating reactive wind slabs on all aspects. 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

Sunday Night

Cloudy with clear periods, trace accumulation, winds east 10 to 15 km/h, treeline temperatures -8 °C.

Monday

A mix of sun and cloud, trace accumulation, winds switching to southeast 10 to 20 km/h, treeline temperatures -10 to -5 °C.

Tuesday

Cloudy with sunny periods, 2 cm accumulation, winds southerly 10 to 20 km/h, treeline temperatures -7 °C.

Wednesday

Mostly cloudy, 2 to 5 cm accumulation, winds southeast 10 to 20 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.