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Avalanche Forecast

Archived

Dec 31st, 2019–Jan 1st, 2020

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.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.

Regions

South Coast.

 Although a slow cooling trend Wednesday is expected to improve avalanche hazard in the aftermath of the storm, continuing snow and wind in the alpine requires managing potentially reactive storm slabs.

Confidence

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

Weather Forecast

Tuesday night: Cloudy, 20-30 cm of snow above 1500 m and rain below, strong southwest winds, alpine temperatures around 4 C with freezing levels dropping from 2200 m.

Wednesday: Mostly cloudy, 3-5 cm of snow, moderate west winds, alpine high temperatures near 2 C with freezing level dropping to 1000 m.

Thursday: Cloudy, 5-10 cm of snow, light west winds, alpine high temperatures near -1 C, freezing level dropping below 500 m.

Friday: Cloudy, 20-30 cm of snow overnight before precipitation changes to rain early morning as freezing levels jump to 2000 m, strong southwest winds, alpine high temperatures near 5 C.

Avalanche Summary

A size 1.5 natural wet loose avalanche was reported during the most recent storm.

Snowpack Summary

Substantial amounts of rain have soaked the existing snowpack up to 2200 m. With forecast freezing levels slowly dropping throughout the day, the overall hazard trend is expected to improve. Above 1500 m, an additional 20-30 cm of snow could fall forming a potentially reactive new slab layer, especially where strong southwest winds drift the new snow into deeper, stiffer slabs.

Snowpack depths near treeline range from 150-200 cm, and the snowpack diminishes rapidly with elevation.

Terrain and Travel

  • Minimize exposure during periods of heavy loading from new snow, wind or rain.
  • Keep in mind that wet avalanches can be destructive due to their high density.

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.