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Avalanche Forecast

Archived

Apr 16th, 2021–Apr 17th, 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 unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

South Rockies.

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

FRIDAY NIGHT: Sunny / light, northeast wind / alpine low 0 / freezing level up to 2700 m possible. 

SATURDAY: Sunny / light northwest wind / alpine high temperature +11 / freezing level 2900 m.

SUNDAY: Cloudy with rain/flurries; 5-10 mm / moderate northeast wind / alpine high temperature +1 / freezing level dropping during the day to 1400 m.

MONDAY: Mostly cloudy / light northerly winds / alpine high +2 / freezing level 1700 m.

Avalanche Summary

The field team didn't notice any new avalanches in the Crowsnest area on Friday. Recent wet loose avalanches have so far been limited to surface snow running on crusts from April and March.

Prolonged warming may increase the sensitivity of deeply buried layers, although there is a fair bit of uncertainty about how likely this is in the South Rockies region. 

There have been some notable slab avalanches reported to the north of the region recently including a skier triggered avalanche in Kananaskis Country on Saturday (see reports here and here) as well as cornice triggered deep persistent slab avalanche in Kootenay National Park on Tuesday (see photo here). These avalanches provide a good reminder of why it's good to be extra cautious during the heat of the day this time of year.

Snowpack Summary

Lingering wind slabs may still be reactive in isolated locations on steep northerly aspects in the alpine that still have dry snow. All other terrain is undergoing a melt-freeze cycle with successive days of warm sunny weather. Things will be "more melt, less freeze" on Saturday as we do not expect a good overnight recovery. 

Strong solar radiation and warming will trigger more wet loose avalanches on Saturday as the snow loses cohesion. Cornices are large and fragile. Cornice falls could trigger avalanches on the slopes below.

The snowpack is overall strong and settled in most areas, however, sustained warming can increase the likelihood of large avalanches failing on deeply buried weak layers.This is most likely to occur on steep, rocky alpine slopes 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.
  • 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.
  • Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.

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.