Avalanche Forecast

Issued: Dec 11th, 2020 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs.

Avalanche Canada ahanna, Avalanche Canada

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Storm slabs sitting over a crust will be especially sensitive to triggering with the sun shining on Saturday.

Summary

Confidence

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

Weather Forecast

Friday night: Clear, light northeast ridgetop wind, freezing level 600 m.

Saturday: Sunny, light variable ridgetop wind, alpine high -1 C, freezing level 1200 m.

Sunday: Around 10 cm new snow, light to moderate southwest wind, alpine high -2C, freezing level 1000 m.

Monday: 10-15 cm new snow, light southwest wind, alpine high -2 C, freezing level 900 m.

Avalanche Summary

As snow fell Friday morning, we received reports of skier controlled loose dry avalanches up to size 1 at Seymour. Touchy remote triggered storm slabs size 1-1.5 were reported on northerly aspects in this great MIN from Pump Peak.

Over the weekend, we expect to see more storm slab avalanche activity as the snow settles in the sun. The underlying crust makes a slick bed surface for avalanches to run on.

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

Check out North Shore Rescue's detailed snowpack conditions report here.

In the North Shore mountains, 20-30 cm of quite low density snow overlies a layer of weak crystals sitting on a monster crust which was formed during the atmospheric river early in the week. As the sun comes out Saturday, rapid settlement and accelerated slab development over the weak layer will make storm slabs more sensitive to triggering. If triggered, the crust makes a fast bed surface for avalanches to run far.

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 changing conditions today, storm slabs may become increasingly reactive.
  • Closely monitor how the new snow is bonding to the crust.
  • Keep in mind the crust offers an excellent bed surface for avalanches.
  • Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.

Problems

Storm Slabs

An icon showing Storm Slabs

Storm slab avalanche activity is expected to increase as 20-30 cm of recent snow settles to form a cohesive slab over a layer of weak crystals ontop of a crust. Be especially cautious of fat, wind loaded pockets in north-northwest terrain features.

There is also potential for loose snow avalanches on steep slopes where the sun touches dry snow for the first time.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 1.5

Valid until: Dec 12th, 2020 4:00PM