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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

South 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: Light flurries bringing trace amounts of new snow with moderate southeast winds. Low of -8 at 2000 m.

 

THURSDAY: Mostly cloudy with light flurries bringing up to 5 cm of new snow with light to moderate southerly winds. Freezing level rising to 2000 m.

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

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

Avalanche Summary

A few size one skier controlled wind slab avalanches were reported on Tuesday. These avalanches were on northerly aspects at or above treeline.

We suspect small pockets of wind slab will remain reactive to rider traffic.

Snowpack Summary

Around 30 cm of recent storm snow overlies a variety of old surfaces including wind effected surfaces, facets and a crust on solar aspects. Below this another melt-freeze crust can be found on all aspects down 30 to 60 cm to 2200 m and mountain tops on solar slopes. 

The late March crust layer is found 50 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.