Avalanche Forecast

Issued: Feb 24th, 2022 4:00PM

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

Avalanche Canada bchristie, Avalanche Canada

Email

Start on smaller features and gather information before jumping into a big, committing line. 

Large avalanches are possible on isolated features in the alpine, and even small avalanches can be dangerous in steep terrain or around terrain traps.

Summary

Confidence

High - We have a good understanding of the snowpack structure and confidence in the weather forecast

Weather Forecast

Thursday Night: Clear. No new snow expected. Moderate west ridgetop wind. Possible temperature inversion could make for temperatures warmer than -5 °C above 1700 m.

Friday: Sunny with scattered clouds. No new snow expected. Moderate southwest ridgetop wind. Possible temperature inversion could make for temperatures warmer than -5 °C above 1700 m.

Saturday: Cloudy. 2 cm of snow expected overnight, and another 2-5 through the day. Strong south ridgetop wind, trending to extreme at higher elevations. Temperature inversion breaking down. Alpine high around -7 °C.

Sunday: Cloudy. 2-5 cm of snow expected overnight, and another 0-5 through the day. Strong to extreme south ridgetop winds. Freezing levels rising to 1000 m in some parts of the region. Alpine high around -5 °C.

Avalanche Summary

No new avalanches were reported on Thursday before 4 pm. 

On Wednesday, an AST course reported some natural windslab avalanches up to size 1.5 in steep alpine features, as well as several, size 1 natural loose dry avalanches, and rider triggered slab avalanches. For more info, see their Mountain Information Network post here. Also, a professional operation northeast of Hazelton reported a few small, natural and rider triggered avalanches in wind effected storm snow at ridge crests, and in steep features.

On Tuesday, a professional operation northeast of Hazelton reported a couple of natural avalanches up to size 2.5 that may have occurred on Monday. They were on north or northeast aspects around treeline, and one was a windslab, while the other was a cornice failure that likely triggered a windslab avalanche on the slope below. 

On Monday, avalanche activity was limited to thin, size 1 wind slabs and loose dry sluffing.

Snowpack Summary

10-20 cm of low density snow overlies a variety of old, generally wind-affected surfaces: Wind pressed snow, sastrugi, windslabs that are slowly bonding to the mid February rain crust, and very wind exposed areas that were stripped back to this crust. See here for a report on alpine conditions in the Hudson Bay backcountry from our Northwest field team.

20-50 cm from the snow surface is a 10-20 cm thick rain crust which effectively caps the underlying snowpack, making human triggering of avalanches on weak layers deeper in the snowpack unlikely, but this crust has been breaking down in some locations, with faceting observed above and below it. Large loads like big chunks of falling cornice may now be able to trigger weak layers below the crust.

Terrain and Travel

  • Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Wind slabs may be poorly bonded to the underlying crust.

Problems

Wind Slabs

An icon showing Wind Slabs

Recent, low density storm snow has been redistributed by moderate to strong west through north winds, forming thin, soft, reactive windslabs, mostly in the alpine.

Older, larger, firmer windslabs sit on top of the mid February rain crust on most aspects. Deeper avalanches failing at this layer are less likely, but could have more serious consequences. Larger triggers like cornice or ice falls have the potential to trigger deeper windslabs.

The most likely place to trigger a wind slab is near ridge crest and on convex terrain features, where the slope rolls away from you. 

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 25th, 2022 4:00PM