Avalanche Forecast

Issued: Dec 13th, 2020 4:00PM

The alpine rating is low, the treeline rating is low, and the below treeline rating is low. Known problems include Wind Slabs.

Avalanche Canada ahanna, Avalanche Canada

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Small, isolated pockets of wind slab sitting on a crust have been triggerable by skier traffic recently. Most likely areas to find these pockets are just beneath ridgecrests and roll-overs.

Summary

Confidence

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

Weather Forecast

Sunday night: Partly cloudy, light northwest ridgetop wind, freezing level valley bottom.

Monday: Partly cloudy, light northwest wind, alpine high -7, freezing level valley bottom.

Tuesday: Up to 5 cm new snow, moderate to strong southwest wind, alpine high -7, freezing level 500 m.

Wednesday: Partly cloudy, moderate southwest ridgetop wind, alpine high -6 C, freezing level 800 m.

Avalanche Summary

Over the last week, avalanche activity has been limited to size 1 skier triggered storm/wind slabs running on the crust. This great MIN from Friday near Nelson includes a photo of an accidental wind slab.

Please submit your observations to the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!

Snowpack Summary

Wednesday's storm deposited 6-20 cm of snow. At low to mid elevations early in the storm, light rain is reported to have destroyed some surface hoar and in most places left a freezing rain crust in its place before things cooled and covered it with the remaining storm snow. 

There is less known about upper elevations where the new snow may have been more wind affected and sit on a variety of surfaces such as crusts, surface hoar and old wind polished snow. If you have found buried surface hoar from December 8th, we would love to hear about it in the Mountain Information Network.

The early November crust is sitting about 10-30 cm up from the ground. There is a late November crust in the midpack in some places as well. Uncertainty with these crusts exist due to limited observations, but there haven't been any recent avalanches reported on these layers in this region.

Snowpack depths vary with elevation, treeline averages between 50-100 cm. 

Terrain and Travel

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Investigate the bond of the recent snow before committing to your line.
  • Use small low consequence slopes to test the bond of the new snow.

Problems

Wind Slabs

An icon showing Wind Slabs

20 cm of snow at upper elevations may sit over a rain crust and/or possibly surface hoar. Human triggering is more likely where the snow had been exposed to wind.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

1 - 1.5

Valid until: Dec 14th, 2020 4:00PM