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Avalanche Forecast

Archived

Dec 28th, 2023–Dec 29th, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

North Columbia, Blue River, Premier, Clemina, Jordan, North Monashee, North Selkirk, Robson.

Uncertainty around persistent weak layers is best managed with conservative terrain choices and minding overhead hazard.

Steep and convex rocky areas are where triggering is most likely.

Confidence

Moderate

Avalanche Summary

On Wednesday, a few large (size 2 to 3) natural and explosive triggered persistent and deep persistent slabs were reported in the alpine. A few smaller (size 1.5) natural windslab and storm slabs have also been seen.

On Tuesday, explosive control in the northern Monashees produced a size 3 deep persistent slab in the alpine and size 2 persistent slab at treeline.

Moving forward, natural avalanche activity has tapered, but large human-triggered slabs remain possible.

Snowpack Summary

Wind affected snow is present on the surface in the alpine and treeline. Below treeline a new crust is on or near the surface.

The mid pack contains several layers of note; a layer of surface hoar and a crust down 20 to 40 cm, a significant crust from the early December rain event down around 50 cm and a layer of surface hoar down 50 to 90 cm.

The make up of the lower snowpack is variable throughout the region, in shallower snowpack areas, basal facets exist. This is most concerning in shallow alpine areas.

Weather Summary

Thursday night

Mainly cloudy with isolated flurries, 1 to 3 cm accumulation. Southwest alpine wind 20 to 40 km/h. Treeline temperature -8 °C.

Friday

A mix of sun and cloud, no new snow. Southeast alpine wind 10 to 30 km/h. Treeline temperature -4 °C.

Saturday

A mix of sun and cloud, no new snow. Southeast alpine wind 10 to 40 km/h. Treeline temperature -2 C, with the potential for an above freezing layer in the alpine up to 2500 m.

Sunday

Mainly cloudy with isolated flurries, 1 to 3 cm accumulation. Southwest alpine wind 10 to 30 km/h. Treeline temperature -2 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Use careful route-finding and stick to moderate slope angles with low consequences.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Overhead hazard may not be obvious, evaluate prior to commiting to terrain.

Problems

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.