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Avalanche Forecast

Archived

Apr 23rd, 2022–Apr 24th, 2022

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

Regions

Yukon.

Assess steep alpine features for wind slab before committing to them. Wind slabs will be most reactive where they overlie a firm crust.

Observations are limited at this time of year! Let us know what you're seeing by posting on the Mountain Information Network.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

SATURDAY NIGHT: Cloudy with a mix of rain and snow, 1 to 5 cm of new snow accumulation at higher elevations. Freezing level dropping to 1000 m. Light to moderate southeasterly winds. 

SUNDAY: Cloudy with continued light precipitation. Freezing level rising to 1400 m. Light to moderate southeasterly winds.

MONDAY: Mainly cloudy with light flurries. Freezing level rising to 1400 m. Light easterly winds.

TUESDAY: Mainly cloudy with light flurries. Freezing level rising to 1400 m. Light to moderate northerly winds.

Avalanche Summary

A large cornice failure was observed in the Cleveland riding area on Thursday. The full report can be seen here.

Looking forward to Sunday, fresh and reactive wind slabs are expected to form in lee areas in the alpine and treeline. Wet loose avalanches will be possible at low elevations with rain and warm temperatures. These avalanches will likely be limited to small releases on isolated slopes in extreme terrain.

Reports are limited at this time of year. Please let us know what you're seeing by filling out a MIN report!

Snowpack Summary

New snow and southerly winds are expected to create fresh deposits of wind slab in the alpine and exposed treeline. This 5-10 cm of new snow overlies a faceted and heavily wind-affected surface from last week's strong northerly winds. Large surface hoar has also been found in sheltered areas. On south and west-facing slopes up to 1400 m, a surface crust from spring sunshine can be found, while other aspects hold dry snow. The mid-snowpack is generally strong, overlying weak basal facets at the base of the snowpack. 

Check out this MIN report from the Yukon Field Team for a picture of conditions prior to the storm.

Terrain and Travel

  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Wind slabs are most reactive during their formation.
  • Wind slabs may be poorly bonded to the underlying 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.