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Avalanche Forecast

Archived

Apr 20th, 2023–Apr 21st, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Coquihalla, Harrison-Fraser, Manning, Skagit.

Assess for wind slabs in steep terrain.

Confidence

High

Avalanche Summary

A few small (size 1) wet loose avalanches were observed out of steep and rocky terrain on Wednesday. Riders also triggered some small (size 1) wind slabs on Tuesday.

Looking forward, new wind slabs could be triggered by riders in lee terrain features from Thursday night's storm. Use plenty of caution along alpine ridges, where cornices may be large.

Snowpack Summary

Around 10 cm of snow is forecast for Thursday night with southwest wind, which may form new wind slabs in lee terrain features. The snow will accumulate over a melt-freeze crust on sun-exposed slopes or 5 to 10 cm of dry snow that overlies a thick and hard crust on shaded aspects.

The remainder of the snowpack is strong with varying hard snow layers and bonded melt-freeze crusts. Cornices are large along many alpine ridges.

Weather Summary

Thursday Night

Cloudy with snowfall, accumulation 10 to 15 cm, 20 to 40 km/h southwest wind, treeline temperature -5 °C, freezing level 1000 m.

Friday

Cloudy with snowfall, accumulation 2 to 5 cm, 20 km/h southwest wind, treeline temperature -4 °C, freezing level 1300 m.

Saturday

Cloudy with trace rain or snow, 30 to 40 km/h southwest wind, treeline temperature -1 °C, freezing level rising to 1900 m.

Sunday

Cloudy with rain or snow, accumulation 5 to 10 cm, 30 to 40 km/h southwest wind, treeline temperature -2 °C, freezing level 2000 m dropping to 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Carefully evaluate steep lines for wind slabs.
  • Use ridges or ribs to avoid areas of wind loaded snow.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.