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Avalanche Forecast

Archived

Dec 13th, 2022–Dec 14th, 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.
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.

Fresh wind slabs are expected to form throughout the day as northwesterly winds redistribute the surface snow into lee areas in the alpine and treeline.

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. 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: 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 the fresh 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

Tuesday night

Clear periods with isolated flurries. Alpine temperatures drop to a low of -9 °C. Ridge wind northeast 10-25 km/h. Freezing level at valley bottom.

Wednesday

Sunny. Alpine temperatures reach a high of -4 °C. Ridge wind 25 km/h gusting to 50 km/h from the northwest. Freezing level at valley bottom.

Thursday

Sunny with cloudy periods. Alpine temperatures reach a high of 1 °C. Ridge wind north 15 km/h gusting to 60 km/h. Freezing level rises to 1800 metres.

Friday

Sunny. Alpine temperatures reach a high of 3 °C. Ridge wind 25 km/h occasionally gusting to 50 km/h. Freezing level rises to 2500 metres.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • 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.
  • 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.