Avalanche Forecast

Archived

Apr 15th, 2021–Apr 16th, 2021

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Lizard-Flathead.

As freezing levels rise, the likelihood for large cornice failures and wet loose avalanches will increase. Start early and plan to be off large slopes before the heat of the day.

Check out the latest Forecaster's Blog for more information on managing current conditions.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

THURSDAY NIGHT: Clear / Moderate, northeast ridgetop wind / alpine low temperature -2 / Freezing level 2100 m.

FRIDAY: Sunny / Light, northeast ridgetop wind / alpine high temperature 10 / Freezing level 2700 m.

SATURDAY: Sunny / Light, northwest ridgetop wind / alpine high temperature 11 / Freezing level 2900 m.

SUNDAY: Cloudy with isolated flurries; 3-5 cm. / Moderate, northeast ridgetop wind / alpine high temperature 1 / Freezing level dropping to 1700 m.

Avalanche Summary

Numerous naturally triggered wet loose avalanches up to size 2.5 were reported near Fernie on Tuesday.

As freezing levels continue to rise and remain elevated overnight, the likelihood for large cornice failures and wet loose avalanches will increase. Cornice failures could trigger deeply buried weak layers on steep, rocky slopes with a shallow or thin to thick snowpack.

Snowpack Summary

Lingering wind slabs may still be reactive in isolated locations on steep northerly aspects in the alpine. All other terrain is undergoing a melt-freeze cycle with successive days of warm sunny weather.

Strong solar radiation and warming will likely trigger the large cornices that hang over ridgelines. Cornice falls could trigger large avalanches on the slopes below.

The snowpack is overall strong and settled, although intense warming could potentially weaken deeper layers in steep, rocky terrain with a shallow or thin to thick snowpack.

The snow line is slowly creeping up the mountains, making some access areas snow-free.

Terrain and Travel

Extra caution is needed around cornices under the current conditions.
Avoid exposure to slopes that have cornices overhead.
As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
Back off slopes as the surface becomes moist or wet with rising temperatures.

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.