Avalanche Forecast

Issued: Mar 22nd, 2020 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 astclair, Avalanche Canada

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New snow drifted by wind may form reactive slabs at upper elevations. Anticipate changing conditions and monitor the depth, cohesiveness, and bond of the new snow to the old snow surface.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Sunday night: Cloudy, up to 5 cm of snow, light southwest wind gusting moderate near ridge-tops, alpine temperature -5 C, freezing level 1000 m.

Monday: Cloudy, 5-10 cm of snow, light southwest wind, alpine temperature -5 C, freezing level 1500 m. 

Tuesday: Mostly cloudy, 5-10 cm of snow, light southwest wind, alpine temperature -7 C, freezing level 1300 m.

Wednesday: Mix of sun and cloud, light west wind, alpine temperature -9 C, freezing level 1100 m. 

Avalanche Summary

Over the past several days, avalanche activity was reported as natural loose wet avalanches (size 1-2) running in steep, sun-exposed terrain. Cornices were also observed failing naturally, primarily on north, northeast, and east aspects.

Over the past week, slab avalanches releasing on buried surface hoar layers were also been reported. Several were attributed to peak warming on solar aspects. These avalanches occurred between 1700 m and 2300 m and were breaking 40-100 cm deep. See this MIN report for a helpful illustration.

If you decide to travel in the backcountry, consider sharing your observations via the Mountain Information Network (MIN) to supplement our data stream as operators are shutting down. A conservative mindset and margins are recommended at this time.

Snowpack Summary

5-15 cm of new snow is forecast to accumulate by Monday afternoon. Moderate southwest winds at ridge-tops may build wind slabs primed for human triggering on lee features.

The new snow is falling on a variety of snow surfaces, consisting of sun crusts, hard wind-affected snow, and soft faceted snow. There have also been reports of surface hoar forming on sheltered, shady slopes. See this MIN for a helpful illustration from nearby Glacier National Park. It will be important to track the depth, cohesiveness, and bond of the new snow to these various old snow surfaces across aspects and elevations where you're travelling.

Cornices are large and looming. Two layers of buried surface hoar can be found buried 20-40 cm deep (March 10) and 60-120 cm deep (February 22). Though there is a low likelihood of triggering an avalanche on these layers, the consequences of doing so would be high. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Make observations and assess conditions continually as you travel.

Problems

Wind Slabs

An icon showing Wind Slabs

Up to 15 cm of new snow may accumulate by Monday afternoon in favored areas. Wind slab avalanches may increase in their sensitivity to human-triggering where moderate southwest winds are loading the new snow into slabs on lee features.

Aspects: North, North East, East, South East, South, West, North West.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 23rd, 2020 5:00PM