Avalanche Canada mconlan, Avalanche Canada

Sea to Sky Avalanche Forecast

Feb 21st, 2020 4:00PM

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

Overnight snow may not bond well to underlying layers. Maintain a conservative mindset and travel cautiously to avoid the problem.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

FRIDAY NIGHT: Cloudy with snowfall, accumulation 10 to 20 cm, moderate to strong southwest wind, alpine temperature -6 C, freezing level 1000 m.

SATURDAY: Mix of sun and cloud, light to moderate northwest wind, alpine temperature -8 C, freezing level 1000 m.

SUNDAY: Cloudy with snowfall, accumulation 15 to 20 cm, moderate to strong southwest wind, alpine temperature -8 C, freezing level 800 m.

MONDAY: Mix of sun and cloud, moderate west wind, alpine temperature -10 C, freezing level 700 m.

Avalanche Summary

No new avalanches were observed on Thursday. Avalanche activity is expected to increase Friday night into Saturday with the new snow that will fall with strong southwest wind.

Snowpack Summary

Around 10 to 20 cm of snow is forecast to accumulate Friday night and it will fall with strong southwest wind. This snow may form storm slabs at all elevations. The slabs will likely be deepest in lee terrain features near ridges. The snow may overly a weak layer of surface hoar crystals 5 mm in size and near-surface facets at treeline and alpine elevations or a melt-freeze crust on sun-exposed aspects.

The midpack is well-settled.

Faceted snow and crusts exist near the base of the snowpack in much of the region. This layer is dormant at the moment but appears to be most likely a problem on the eastern side of the region, in alpine terrain, and where there is relatively smooth ground (e.g., glaciers, scree slopes, rock slabs).

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Choose conservative terrain and watch for clues of instability.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Likely

Expected Size

1 - 2

Friday night's snowfall likely won't bond well to underlying layers, as it will fall into a weak layer of surface hoar or faceted grains at and above treeline, or a melt-freeze crust on sun-exposed slopes. The slabs will be deepest in lee terrain features near ridges, as the snow fell with strong southwest wind.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Feb 22nd, 2020 5:00PM