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Avalanche Forecast

Archived

Apr 21st, 2023–Apr 22nd, 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, human triggered possible.
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.

Check for signs of windslab instability in steep terrain at higher elevations, especially around ridgetops. Shooting cracks or fresh avalanches are signs that you should retreat to terrain that is not exposed to the wind.

Confidence

Moderate

Avalanche Summary

A few small (size 1) dry loose avalanches were observed out of steep, rocky terrain on Friday.

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, wind slabs could be triggered by riders in lee terrain features from Thursday night's storm, and continued moderate southwest wind.

Use plenty of caution along alpine ridges, where cornices may be large.

Snowpack Summary

10-15 cm of snow fell Thursday night. Moderate southwest wind during the storm and continuing through Saturday will keep building wind slabs in lee terrain features. This recent snow sits 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.

Rising freezing levels on Saturday mean that the surface snow could get dense and moist at treeline and below.

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

Friday Night

Cloudy. Trace of snow expected. Snow/rain line around 1000 m. Treeline temperature around -5 °C. Light to moderate southwest ridgetop wind.

Saturday

Cloudy. No new snow expected. Freezing level rising to 1700 m. Treeline high around 0°C. Light to moderate southwest ridgetop wind.

Sunday

Cloudy. Moderate rainfall, 5-10 mm. Snow/rain line falling from 2000 to 1500 m. Light to moderate southwest ridgetop wind.

Monday

Cloudy. Light snow/rain expected. Snow/rain line rising from 1000 to 1500 m. Light variable ridgetop wind.

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.