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Avalanche Forecast

Archived

Dec 14th, 2020–Dec 15th, 2020

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

Regions

South Coast.

Heavy snowfall and strong southwest winds are forming reactive slabs. It's a good day to stick to conservative terrain.

Confidence

Moderate -

Weather Forecast

Monday night: 10-20 cm new snow, wind increasing to strong southwest, freezing level 800 m.

Tuesday: 10-20 cm new snow, strong southwest ridgetop wind, alpine high -2 C, freezing level 1200 m.

Wednesday: 15-20 cm new snow, moderate to strong southwest ridgetop wind, alpine high 0 C, freezing level 1300 m.

Thursday: 20-25 cm new snow overnight, moderate northwest wind, alpine high 0 C, freezing level 1300 m.

Avalanche Summary

On Friday and Saturday, we received reports of natural and skier controlled loose dry size 1 and storm slabs size 1-1.5. See photos of some touchy remote triggered slabs during the storm Friday in this great MIN from Pump Peak. 

Have you been out and about in the mountains? If so please submit your observations to the Mountain Information Network (MIN). It doesn't have to be technical - photos are especially helpful! Thank you so much for all the great MINs submitted so far!

Snowpack Summary

20-40 cm falling on the North Shore mountains by end of the day Tuesday brings storm totals to 30-60 cm. This recent snow sits on a thin melt freeze crust on solar aspects, and possibly over a layer of weak surface hoar crystals in wind sheltered areas. This MIN from Saturday includes photos of the surface hoar before it was buried.

A layer of weak crystals sitting on a 20 cm thick crust is now covered by 40-80 cm of snow. We have had our eyes on it since it became buried last week. We haven't seen any avalanches on this layer since Saturday and snowpack tests since Sunday have shown no results at this interface.

We have very little data and a lot of uncertainty around alpine conditions in the region. If you go out in the mountains, please let us know what you see via the Mountain Information Network (MIN). 

Terrain and Travel

  • Watch for fresh storm slabs building throughout the day.
  • As the storm slab problem gets trickier, the easy solution is to choose more conservative terrain.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.

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.