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Avalanche Forecast

Archived

Apr 20th, 2022–Apr 21st, 2022

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

North Columbia.

Continue to assess the wind slab hazard as you gain elevation.

Confidence

Moderate - The snowpack structure is generally well understood.

Weather Forecast

Wednesday night: No new snow expected. Light southeast winds and a low of -8 at 2000 m.

 

THURSDAY: Mostly cloudy with flurries bringing trace amounts of new snow with light southeast winds. Freezing level rising to 1900 m.

Friday: Mostly cloudy with flurries bringing up to 10 cm of new snow with light northwest winds. Freezing level around 2000 m.

Saturday: Sunny with no new snow expected. Light northwest winds and freezing levels rising to 2200 m.

Avalanche Summary

On Tuesday skier traffic produced numerous size one storm and wind slab avalanches at treeline and above.

We suspect that small wind slab avalanches will remain possible. 

Snowpack Summary

15 to 30 cm of new snow overlies a variety of surfaces including old wind effected surfaces, facets and a crust on solar aspects. Below this another melt-freeze crust can be found down 20 to 50 cm on all aspects to 2000 m and mountain tops on solar aspects. 

The late March crust layer is found 40 to 90 cm deep.

Cornices are very large and exposure to slopes beneath them should be minimized, especially if the weather is sunny, warm, or windy. The snowpack deteriorates rapidly at lower elevations.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Closely monitor how the new snow is bonding to the crust.
  • 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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.