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Avalanche Forecast

Archived

Apr 5th, 2021–Apr 7th, 2021

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

Regions

North Rockies.

Wintery weather returns with new snow expected to form unstable slabs on steep open slopes this week.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

MONDAY NIGHT: Cloudy with some isolated flurries, 40 km/h west wind, treeline temperatures drop to -5 C.

TUESDAY: Cloudy with scattered flurries and up to 5 cm of snow, 30 km/h southwest wind, freezing level climbs to 1400 m with treeline temperatures around -3 C.

WEDNESDAY: Scattered flurries with 10 cm of snow for most parts of the region and up to 20 cm in the McGregors and Renshaw areas, 40 km/h southwest wind, treeline temperatures around -5 C.

THURSDAY: Mostly cloudy skies, 30-50 km/h southwest wind, treeline temperatures around -5 C.

Avalanche Summary

On Saturday the North Rockies field team reported a wind slab avalanches on an east-facing slope at Renshaw that was a few days old. Otherwise the only other recent reports of avalanches have been from a natural cycle of storm slab avalanches that occurred at the end of March in northern parts of the region.

Snowpack Summary

A frontal system crossing the region on Wednesday will deliver 5-20 cm of new snow above 1200 m. This adds to 15-20 cm of recent snow in southern parts of the region and 5-10 cm in northern parts of the region. Overall this snow is settling relative quickly, but unstable slabs may be found on wind loaded features. Recent snow sits on crusts at lower elevations and on solar aspects. 

Recent weather patterns have helped previous weak layers strengthen, including the mid-February facet layer that is now roughly 150 cm deep. However, it may still be possible to trigger avalanches on basal layers in shallow rocky terrain along the eastern slopes of the Rockies.

Terrain and Travel

  • Use ridges or ribs to avoid areas of wind loaded snow.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Be alert to conditions that change with aspect and elevation.
  • 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.