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Avalanche Forecast

Archived

Nov 30th, 2020–Dec 1st, 2020

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

Regions

South Coast.

Avalanche danger will rise to CONSIDERABLE in the afternoon as temperatures rise at upper elevations. Use extra caution where recent snow is experiencing sun and rapidly warming temperatures for the first time.

Confidence

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

Weather Forecast

Monday night: Clear, light northwest wind, freezing level 800 m.

Tuesday: Clear, light northwest wind, freezing level spiking in the afternoon 800 to 3000 m.

Wednesday: Sunny, moderate southeast wind, freezing level 3000 m.

Thursday: Sunny, moderate south wind, freezing level 1800 m.

Avalanche Summary

Tuesday we may see storm slab avalanches due to rapidly warming temperatures and sun in the afternoon. They may be especially reactive where recent snow sits over a crust. Loose wet avalanches are also be possible, especially on steep solar aspects. 

Our eyes and ears in the mountains are limited at this time of year and may continue this winter due to fewer professional observations. If you see anything (or don't) while out in the field, please consider sharing via the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!

Snowpack Summary

Around 30 cm of recent snow and southwest winds have formed fat pockets of storm slab in lee features at upper elevations. Elevations above 1400 m where dry snow fell will feel the greatest impact from rapidly warming temperatures Tuesday afternoon. Below 1200 m, most of the recent snow fell as rain on a soggy snowpack.

The snow line currently sits at around 900 m. Snowpack depth rapidly changes with elevation. The snowpack rapidly jumps to around 100 cm deep above 1000 m and between 150 to 200 cm near the mountain tops.

Terrain and Travel

  • Extra caution for areas experiencing rapidly warming temperatures for the first time.
  • Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
  • Be cautious of buried obstacles especially below treeline.

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.