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Avalanche Forecast

Archived

Dec 19th, 2023–Dec 20th, 2023

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

Glacier.

Sniffing out bold lines on untracked slopes with exposure has caught a number of folks by surprise, resulting in several near-misses.

A weak layer primed for human triggering continues to produce isolated large avalanches. The safest way to manage this problem is through conservative terrain use.

Confidence

Moderate

Avalanche Summary

Five significant human-triggered avalanches have occurred in the past week, all failing on the Dec 1st surface hoar layer. In the Connaught drainage a size 2.5 was triggered on Balu Peak, on Ursus Minor a skier narrowly avoided being carried over some cliffs, and in the Asulkan valley another avalanche was triggered near the 7 steps. East of the park an experienced group triggered a size 2 avalanche on the same layer with one skier partially buried.

Snowpack Summary

20cm of soft snow overlies variable old surfaces: wind affect; a thin sun crust on steep, solar slopes; or surface hoar in sheltered treeline areas.

The Dec 1 surface hoar, down 50-100cm, continues to produce 'sudden' results in snowpack tests and has been the culprit in several recent human-triggered slides. Below 2100m, a rain crust is buried 40-50cm deep.

In shallow areas the base of the snowpack is faceted and unsupportive.

Weather Summary

No major storms on the horizon, with only minor blips making it to the Selkirks.

Tonight: flurries, 5cm, Alp low -3°C, mod SW winds, 1600m freezing level (fzl)

Wed: Cloudy with flurries, 5cm, Alp high -2°C, mod SW winds, 1600m fzl

Thurs: Cloudy, isolated flurries, Alp high -2°C, light SW winds, 1600m fzl

Fri: Flurries, 5cm, Alp high -3°C, light SW winds, 1400m fzl

Terrain and Travel Advice

  • Be mindful that deep instabilities are still present and have produced recent large avalanches.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Problems

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.

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.