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Avalanche Forecast

Archived

Dec 14th, 2022–Dec 15th, 2022

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

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

Northerly winds have formed stiff wind slabs in unusual areas and at lower elevations than you might typically expect. These slabs are expected to bond poorly to the underlying crust.

Conservative terrain selection and good travel habits will be essential to manage the developing deep persistent slab problem.

Confidence

Moderate

Avalanche Summary

On Monday near Pemberton, a skier-triggered persistent slab avalanche occurred on a northwest aspect in the alpine. The bed surface of this avalanche was reported as a crust with large surface hoar above. Interestingly, this avalanche triggered a size 2 in adjacent terrain, which failed on facets and depth hoar near the ground level. This avalanche is a sign pointing toward a developing deep persistent slab problem in this region.

Observations are limited this time of year. Please keep posting your observations to the MIN; it helps strengthen our information gathering.

Snowpack Summary

In deeper zones at 1900 m, the snowpack is around 100-130 cm, which is low for the middle of December, and it has a weak structure.

Surface: Large surface hoar has been reported in sheltered areas. A crust exists on solar aspects. Boot top powder in deep areas. Same old crusts, facets, and rocks on wind-scoured slopes. Wind slab pockets lee of ridges. Upper-pack: Below last week's new snow is well-developed surface hoar in sheltered areas. The upper part of the snowpack is generally low density and faceting (aka weak).Mid-pack: maybe a crust or two, with a layer of soft facets above. This is likely the primary weak layer.Lower-pack: facets and depth hoar (aka not strong).

Weather Summary

Wednesday night

Clear with cloudy periods. Alpine temperatures drop to a low of -5 °C. Ridge wind 25 km/h occasionally gusting to 55 km/h. Freezing level at valley bottom.

Thursday

Sunny with cloudy periods. Alpine temperatures reach a high of -1 °C. Ridge wind 20 km/h occasionally gusting to 55 km/h from the north. Freezing level at valley bottom.

Friday

Sunny with cloudy periods and an alpine temperature inversion. Alpine temperatures reach a high of 3 °C. Ridge wind 25 km/h occasionally gusting to 40 km/h from the north. Freezing level rises to 2500 metres.

Saturday

Sunny with cloudy periods. Alpine temperatures reach a high of -6 °C. Mostly light ridge wind occasionally gusting to 35 km/h from the southwest. Freezing level at valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid freshly wind loaded terrain features.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • The best and safest riding will be on slopes that have soft snow without any slab properties.

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.