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Avalanche Forecast

Archived

Dec 2nd, 2021–Dec 3rd, 2021

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 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

Northwest Coastal.

Wind slabs can still be triggered by riders. Also be aware that rapidly forming wind and storm slabs can naturally avalanche.

Monitor wind and new snowfall as you travel through terrain, and make more conservative choices if you find signs of instability.  

Confidence

Moderate - We are confident about the likelihood of avalanche activity, what is less certain are their possible size.

Weather Forecast

Thursday Night: Overcast with potential breaks in cloud. 0-5cm new snow. Strong southwest wind. Alpine temperature around -13 C.

Friday: Mostly overcast. 5-15 cm new snow. Strong southwest wind. Alpine temperature around -12 C.

Saturday: Partly Cloudy. Possible trace of new snow. Moderate northwest wind. Alpine temperature around -14 C.

Sunday: Mostly Cloudy. 0-5 cm of new snow possible in the afternoon. Moderate southwest wind. Alpine temperature around -12 C.

Avalanche Summary

On Wednesday morning, a few small natural avalanches were observed and explosive and machine control work produced size 1-2 storm slab avalanches.

Near Stewart, there is evidence that a widespread avalanche cycle occurred during the past storm, up to size 3 in wind loaded terrain at treeline and in the alpine. 

On Tuesday morning, several size 2 storm slabs were reported to have run naturally during the storm.

Snowpack Summary

Up to 30 cm of snow in the last 36 hours continues to be redistributed and built into slabs by moderate to strong winds. The most recent snow is less dense than the last week, but it can still form reactive slabs.

The new snow overlies a variable surface produced by the previous, warmer, wetter, windier storms. Snow had been stripped from ridgetops and exposed terrain and loaded into lee terrain features and cross-loaded slopes by strong to extreme wind at upper elevations. At elevations below treeline where the snow hasn't been washed away altogether, expect to find a crust under the new snow.

A crust that formed as high as 1600 m during a previous warm November storm is now 60-100 cm deep. Wind slabs have shown good propagation where they sit directly over this slick sliding surface.

In the Northern part of the region (Bear Pass) two weak layers of surface hoar from early to mid November have been reported in sheltered areas at treeline.

Treeline snowpack depths are estimated to be around 2-3 m, and a prominent crust can be found near the base of the snowpack.

Terrain and Travel

  • Be alert to conditions that change with elevation and wind exposure.
  • Avoid lee and cross-loaded slopes at and above treeline.
  • A crust on the surface will help bind the snow together, but may make for tough travel conditions.
  • Keep in mind the crust offers an excellent bed surface for avalanches.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.