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Avalanche Forecast

Archived

Dec 9th, 2024–Dec 10th, 2024

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

Regions

Glacier.

~65cm of snow overlies surface hoar or a sun crust; both problematic persistent layers that promote poor bonding, remote triggering, and easy sliding.

Human triggered avalanches are possible to likely on slopes that did not previously avalanche during the storm, especially where the surface feels "slabby".

Confidence

Moderate

Avalanche Summary

Natural avalanche activity has curtailed in the last 24hrs, with a few loose/dry sz 1-1.5 avalanches observed in the highway corridor in steep/extreme.

Artillery control produced excellent results on Tupper and Macdonald Sat night, with most shots producing sz 2 to sz 3 avalanches from steep start zones, running out onto valley bottom fans. Debris moved fast, likely picking up speed and mass on the buried surface hoar.

Snowpack Summary

Up to 65cm of new snow sits on a sun crust on steep solar aspects. In sheltered locations, this new snow sits atop large surface hoar. Strong SW winds at the end of the storm created surface slab conditions on exposed Treeline and Alpine slopes.

There is a dense, well-settled mid-pack without any significant weak layers.

The Nov 9 crust is down 1-1.5m. The base of the snowpack is comprised of several dense, melt-freeze rain crusts formed in October.

Weather Summary

The ridge of high pressure continues, with no significant change in the weather.

Tonight: Mainly cloudy, Alp low -11°C, light W winds, Freezing Level (FZL) 500m.

Tues: Cloudy with sunny periods, Alp high -7°C, light W winds, FZL 800m.

Wed: Clouds, isolated flurries, Alp high -4°C, light SW winds, FZL 1500m.

Thurs: Cloudy, isolated flurries, Alp high -4°C, light S winds, FZL 1300m.

Terrain and Travel Advice

  • Be aware of the potential for remote triggering and large avalanches due to buried surface hoar.
  • Make conservative terrain choices and avoid overhead hazard.
  • Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.

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.