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Avalanche Forecast

Archived

Dec 29th, 2020–Dec 30th, 2020

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
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.

Regions

South Coast.

A big storm is expected to bring up to 50 cm of new snow by Wednesday evening. Avoid avalanche terrain for now, as a widespread avalanche cycle is expected.

Confidence

Moderate - Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

TUESDAY NIGHT - Snow, 10-20 cm / southwest wind, 30-60 km/h, gusting to 80 km/h / alpine low temperature near -2 

WEDNESDAY - Snow, mixed with rain at times, 25-30 cm / southwest wind, 40-60 km/h, gusting to 80 km/h / alpine high temperature near 0 / freezing level rising to 1000 m 

THURSDAY - Mainly cloudy / light northwest winds / alpine high temperature near 0 / freezing level 1200 m

FRIDAY - Snow and rain, 30-50 cm / southwest wind, 60-80 km/h / alpine high temperature near 1 / freezing level 1500 m 

Avalanche Summary

Stormy weather overnight Tuesday and into Wednesday will likely result in a natural avalanche cycle. Steer clear of avalanche terrain for now.

Snowpack Summary

10-20 cm overnight Tuesday followed by up to 30 cm on Wednesday will mean that storm slabs will be widespread, and easy to trigger.

This new snow will land on 30-70 cm recent storm snow which appears to be adhering well to old surfaces. 

Around 80-130 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. It seems to be bonding well with surrounding snow.

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

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.