Avalanche Forecast

Archived

Apr 21st, 2021–Apr 23rd, 2021

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

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.

A spring diurnal pattern dominates. Avalanche danger will be lowest during overnight cool conditions and may increase during the heat of the day.

Confidence

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

Weather Forecast

WEDNESDAY NIGHT: Clear skies, 20 km/h northeast wind, alpine temperature -6 C.

THURSDAY: Clear skies, 20 km/h northeast wind, alpine temperature -4 C, freezing level 1000 m.

FRIDAY: Mix of sun and cloud, 20 km/h northeast wind, alpine temperature -4 C, freezing level 1100 m.

SATURDAY: Mix of sun and cloud, 20 km/h northeast wind, alpine temperature -3 C freezing level 1200 m.

Avalanche Summary

There is widespread evidence of avalanche activity from the warm air temperature last weekend, including large loose wet avalanches and wet slab avalanches. Check out this MIN for a few photos.

Snowpack Summary

A dusting of snow overlies a hard melt-freeze crust to the mountain tops from recent warm air and sunny skies. The snow may moisten during the heat of the day, particularly on sun-exposed slopes and on all aspects below the freezing level.

The White Pass area has a deep snowpack without any layers of concern. A thinner and weaker snowpack exists in inland regions, such as the Wheaton Valley.

Terrain and Travel

Avoid travelling on slopes below cornices.
Back off slopes as the surface becomes moist or wet with rising temperatures.
If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.

Problems

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.

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.