Avalanche Forecast

Issued: Dec 2nd, 2020 4:00PM

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

Avalanche Canada swerner, Avalanche Canada

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The snowpack doesn't like rapid change. The avalanche danger remains elevated due to sustained warm temperatures. Watch for signs of instability and be conservative with your terrain selection.

Summary

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Spring temperatures in December?

Thursday: Mainly cloudy with some sunny periods. Alpine temperatures near +3 and ridgetop wind 20-30 km/hr from the southwest. Freezing levels 2300 m. 

Friday: A mix of sun and cloud. Alpine temperatures near +6 and ridgetop wind moderate from the southwest. Freezing levels 1400 m.

Saturday: Cloudy with sunny periods and light precipitation. Alpine temperatures near +6 and ridgetop wind moderate to strong from the South. Freezing levels 2300 m. 

Avalanche Summary

On Wednesday, a natural widespread loose wet avalanche cycle up to size 1 was reported. I suspect there to be more activity with the associated intense warming.

On Tuesday afternoon numerous size 1-1.5 wet loose avalanches from steep south aspects were reported. A large natural avalanche size 2-2.5 from a north-facing alpine slope was also reported and likely occurred Monday night. 

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

It's a very dynamic period and the snowpack doesn't like rapid change.

Recent sun and warm air well into the alpine on Wednesday likely had the greatest impact on the upper snowpack, showing signs of instability and promoting further slab development and cohesion. This may be most concerning where these slabs sit above an old thin crust on south aspects and feathery surface hoar crystals in wind-sheltered areas. Northerly aspects will likely see fresh wind slab development at upper elevations on leeward slopes and melt-freeze conditions may exist on most aspects and elevations. 

The snowpack depth varies substantially with elevation. Below treeline 30 to 70 cm, 80 to 100 cm near treeline, and around 150 cm may be found in the alpine.

The mid to lower snowpack contains a series of crusts, the most notable of which is also the deepest, sitting just above the ground at elevations above 1500 m. This crust may have a thin overlying layer of weak faceted grains and/or surface hoar crystals, especially in sheltered areas around treeline. There is uncertainty as to whether these layer will be a concern going forward. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

Problems

Wind Slabs

An icon showing Wind Slabs

Recent strong southerly winds have likely redistributed snow at upper elevations, building new wind slabs on leeward northerly facing terrain. The warm air coupled with solar radiation from Wednesday may have promoted rapid settlement and accelerated slab development in the recent storm snow on other aspects and elevations. Be especially cautious where new snow may sit over a crust (south aspects) or surface hoar (wind sheltered areas around treeline).

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Loose Wet

An icon showing Loose Wet

Continued warm temperatures may release loose wet avalanches. Pinwheeling is a good indicator of this type of instability. 

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 3rd, 2020 4:00PM