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Avalanche Forecast

Archived

Apr 21st, 2022–Apr 22nd, 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, 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

South Columbia.

Carefully assess new snow amounts. The size and likelihood of wind slab avalanches will be greatest in localized areas that receive more than 15 cm of new snow.

Confidence

Moderate - Uncertainty is due to the track & intensity of the incoming weather system.

Weather Forecast

Thursday night: around 10 cm of new snow expected with localized areas in the north receiving up to 20 cm of new snow. Light to moderate west winds. Low of -4 at 2000 m.

Friday: A mix of sun and cloud with the possibility of light flurries bringing trace amounts of new snow. Light northwest winds and freezing levels rising to 2000 m.

Saturday: A mix of sun and cloud with the possibility of light flurries bringing trace amounts of snow. Light variable winds and freezing levels rising to 2300 m.

Sunday: A mix of sun and cloud with no new snow expected. Light south winds and freezing levels around 2300 m.

Avalanche Summary

On Wednesday several natural wind slab avalanches up to size 2.5 were observed in the region. Small wet loose avalanches were also observed on solar aspects.

We suspect that rider triggerable wind slab will still be found in exposed treeline and alpine terrain.

Snowpack Summary

On north aspects above 2000 m Around 30 cm of recent storm snow overlies a variety of old surfaces including wind effect and facets. Several crusts exist on solar aspects extending to mountain tops.

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.