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Archived

Avalanche Forecast

Dec 13th, 2020–Dec 14th, 2020
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: South Coast.

Soft storm slabs may be reactive in wind sheltered areas where the new snow sits on a layer of weak surface hoar crystals. 

Confidence

Moderate -

Weather Forecast

Sunday night: Trace to 5 cm new snow, light southwest ridgetop wind, alpine high -2C, freezing level 800 m.

Monday: Trace to 5 cm new snow, light to moderate southwest ridgetop wind, alpine high -2 C, freezing level 1000 m.

Tuesday: 20-30 cm new snow, strong southwest ridgetop wind, alpine high -1 C, freezing level 1200 m.

Wednesday: 10-15 cm new snow, moderate southwest ridgetop wind, alpine high -1 C, freezing level 1400 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

15-20 cm of new new snow sits over a layer of weak surface hoar crystals in wind sheltered areas. This great MIN 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 20-50 cm of snow. In snowpack tests conducted Saturday, this layer popped and slid off with moderate loading. This interface is most likely healing quickly with mild temperatures and under the weight of the snow but if triggered, the crust makes a slick bed surface for avalanches.

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

  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Be aware of the potential for large avalanches due to the presence of a buried crust.
  • Keep in mind the crust offers an excellent bed surface for avalanches.

Avalanche Problems

Storm Slabs

Storm slabs may be especially reactive in wind sheltered terrain where storm snow sits on surface hoar. Caution around wind loaded pockets just below ridge crests and roll-overs. Loose dry sluffing is likely under your skis in steep terrain.

We are uncertain about the potential for step-down avalanches on the buried crust. If triggered, these slabs could be up to 50 cm deep in some places. A crust offers a slick bed surface for avalanches to run fast and far.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 1.5