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Avalanche Forecast

Archived

Dec 21st, 2020–Dec 22nd, 2020

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

Regions

South Coast.

The recent snow may slide easily where it overlies a smooth and hard crust.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

MONDAY NIGHT: Clear skies, 40 km/h northwest wind, treeline temperature -2 C, freezing level 800 m.

TUESDAY: Clear skies, 10 to 20 km/h north wind, treeline temperature -2 C, freezing level 800 m.

WEDNESDAY: Clear skies, 10 km/h northwest wind, treeline temperature -1 C, freezing level 700 m rising to 2000 m.

THURSDAY: Clear skies, 20 km/h southeast wind, treeline temperature 5 C, freezing level 2200 m.

Avalanche Summary

Monday's snow was described as being moveable on the hard melt-freeze crust, forming small avalanches. Otherwise, a recent MIN reporter describes a storm slab avalanche out of steep, southerly terrain near Mt. Seymour on Sunday.

Snowpack Summary

Around 20 cm of snow came out of Monday's storm, which fell onto a hard melt-freeze crust up to around 1500 m. At lower elevations, the wet snow may not have frozen so the new snow may sit on soggy snow. The recent snow may slide easily where it sits on a crust. Above around 1500 m, wind slabs would be the primary concern from substantial recent snowfall and strong wind from variable directions. Cool air temperature may allow for these problems to linger for longer than is typical for the South Coast region.

There are numerous other melt-freeze crusts buried in the snowpack, but no recent avalanches or concerning snowpack test results have been observed around them.

Terrain and Travel

  • Closely monitor how the new snow is bonding to the crust.
  • Watch for areas of hard wind slab on alpine features.
  • Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.

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.