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Avalanche Forecast

Archived

Apr 23rd, 2023–Apr 24th, 2023

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

Regions

Coquihalla, Harrison-Fraser, Manning, Skagit.

Use good travel habits, and evaluate each slope on a case by case basis.

Look for signs of wind slab or wet loose instability before committing to large or steep terrain features.

Confidence

Moderate

Avalanche Summary

On Saturday and Sunday in the Coquihalla area, daytime warming caused numerous naturally triggered wet loose avalanches in steep terrain. The largest of these avalanches was a size 2.

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

Snowpack Summary

A dusting of dry snow covers a mixed bag of surfaces. In the alpine: dry, settling snow on shaded aspects, and moist snow on solar aspects. At treeline and below: moist snow or frozen crusts.

Southwest wind has likely formed wind slabs on leeward terrain features in the high alpine, but field observations are limited.

The recent snow sits over a series of moist or wet layers that have been frozen and thawed again a few times.

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

If you are wondering why the freezing line and the snow line might be so different on some days, click here for more information:)

Sunday Night

Cloudy. Light snow/rain, 2-5 mm, up to 10mm in the southwest corner of the forecast area, close to Chilliwack. Snow/rain line around 1100 m. Treeline low around -3°C. Moderate southwest ridgetop wind.

Monday

Low cloud. Light snow/rain expected. as much as 7 mm in the southwest corner of the forecast area, close to Chilliwack. Snow/rain line around 1250 m. Treeline high around -1°C. Light to moderate west or southwest ridgetop wind.

Tuesday

Mostly sunny by the afternoon. Trace of snow/rain expected. Freezing level rising to between 1800 and 2200 m. Light to moderate southwest ridgetop wind.

Wednesday

Mostly sunny, increasing cloud through the day. No new snow/rain expected. Freezing level rising to 3000 m. Moderate to strong west or southwest ridgetop wind.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Pay attention to isolated alpine features as well as cross-loaded features at treeline.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
  • Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.
  • 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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.