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Avalanche Forecast

Archived

Dec 23rd, 2020–Dec 24th, 2020

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

Regions

South Coast.

Warm air may make the recent snow above the crust easy to trigger in steep terrain.

Confidence

High -

Weather Forecast

WEDNESDAY NIGHT: Clear skies, 20 km/h southwest wind, treeline temperature 0 C, freezing level 2500 m.

THURSDAY: Clear skies, 20 km/h southwest wind, treeline temperature 2 C, freezing level 2500 m.

FRIDAY: Cloudy with rain or snow, accumulation 10 mm or 10 cm, 20 km/h southeast wind, treeline temperature 1 C, freezing level 1600 m.

SATURDAY: Cloudy with snowfall, accumulation 20 to 30 cm, 40 km/h south wind, treeline temperature 0 C, freezing level 1300 m.

Avalanche Summary

Two skier-triggered avalanches were observed on Tuesday within the recent storm snow, as seen in the MINs here and here. The likelihood of triggering similar avalanches will remain possible until we see evidence that the snow is bonding to the underlying crust.

Snowpack Summary

Around 20 cm of snow overlies a hard melt-freeze crust up to around 1500 m. During this period of warm air temperature, the surface snow may rapidly form slabs that could slide easily on the crust. At the mountain tops, the snow may have been blown into thicker and touchy wind slabs on all slopes due to variable wind directions.

The remainder of the snowpack is well-settled and hosts numerous other melt-freeze crusts.

Terrain and Travel

  • Closely monitor how the new snow is bonding to the crust.
  • Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
  • 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.