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Avalanche Forecast

Archived

Dec 7th, 2021–Dec 8th, 2021

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

South Coast.

New snow and wind will form fresh slabs at upper elevations. A couple of near-surface crusts offer slick sliding surfaces for avalanches. As the storm slab problem gets trickier, the easiest solution is to choose more conservative terrain.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

Tuesday: Rain turning to snow 15-20 cm. Strong southwest wind. Freezing level 1500 m and dropping.

Wednesday: A mix of sun and cloud. Strong southwest wind. Treeline high temperatures around -5. Freezing level 800 m.

Thursday: A mix of sun and cloud. Light northwest wind. Treeline high temperatures around -5. Freezing level 500 m.

Friday: New snow 10-15 cm. Strong southwest wind. Treeline high temperatures around -3. Freezing level 700 m.

Avalanche Summary

No recent reports.

Snowpack Summary

15-20 cm of overnight snow fell amid strong wind, likely loading deeper deposits into lee features at upper elevations. The new snow may sit over a thin lens crust that formed when 10-15 cm of recent snow warmed up on Tuesday. This recent snow may be sitting over a weak layer of surface hoar crystals near or on a thick crust. See photos of the surface hoar before it was buried in this excellent MIN report from Sunday.

Treeline snow depths in advance of the atmospheric river were around 80-100 cm but rain has eroded some of this. Much of treeline and almost all below treeline elevations are still below threshold depths for avalanches.

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • 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.