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Avalanche Forecast

Archived

Dec 26th, 2020–Dec 27th, 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 possible, human triggered probable.
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

South Coast.

Recent storm snow will likely remain sensitive to human triggers Sunday, especially if the sun comes out. Be cautious around freshly wind loaded terrain features at upper elevations and watch for signs of loose wet avalanches at elevations where temperatures rise above freezing.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Saturday night: Around 5 cm new snow, moderate south wind, treeline temperature -3 C, freezing level 1000 m.

Sunday: Clearing, light to moderate southwest wind, treeline temperature -2 C, freezing level rising to 1500 m.

Monday: Sunny, light northwest wind, treeline temperature 0 C, freezing level 1800 m.

Tuesday: Increasing cloud, moderate northwest wind switching to southwest, treeline temperature -3 C, freezing level 1000 m.

Avalanche Summary

On Saturday, we received reports from the North Shore mountains of several skier controlled wet loose size 1 and a skier remote size 1 wet slab on a steep unsupported roll. Some whumphing was observed but very little propagation within the storm snow.

Snowpack Summary

30-50 cm of new snow came in warm and wet before freezing levels dropped and the snow started to pile up. With a temperature trend like this, new snow is expected to adhere well to old surfaces. At 1200 m, the snow was reported to be heavy and wet on Saturday afternoon. At higher elevations where dry snow fell, strong winds are expected to have deposited deep pockets of storm slab into lee terrain features.

Around 50-100 cm of snow now overlies a hard melt-freeze crust up to around 1500 m. This layer varies so widely in depth due to the wind transport of snow as it fell over the last two storms.

The remainder of the snowpack is well-settled and hosts numerous other melt-freeze crusts which are well bonded to the surrounding snow.

Terrain and Travel

  • The new snow may require another day to settle and stabilize.
  • Be carefull around freshly wind loaded features.
  • Brief periods of sun could quickly initiate natural avalanche activity.

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.