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Avalanche Forecast

Archived

Mar 15th, 2021–Mar 16th, 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.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Kootenay Boundary.

Daytime warming may weaken cornices and sun-exposed slopes. Best to get off steep slopes before they moisten and watch your overhead exposure.

Confidence

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

Weather Forecast

MONDAY NIGHT: Clear skies, 10 km/h west wind, alpine temperature -3 C.

TUESDAY: Clear skies, 10 km/h southwest wind, alpine temperature -1 C, overnight freeze and daytime freezing level rising to 1900 m.

WEDNESDAY: Clear skies, 10 km/h south wind, alpine temperature 0 C, overnight freeze and daytime freezing level rising to 2000 m.

THURSDAY: Mix of sun and cloud, 30 km/h south wind, alpine temperature 0 C, overnight freeze and daytime freezing level rising to 2000 m.

Avalanche Summary

A few small wet loose avalanches were observed out of steep sun-exposed terrain on Sunday. Similar activity is possible this week during a diurnal cycle.

Snowpack Summary

We are in the midst of a diurnal cycle, where the snow surface will freeze into a melt-freeze crust at night and moisten during daytime heating, particularly on sun-exposed slopes. Dry, settled snow may still exist near the mountain tops on northerly aspects. Cornices are large and always have the potential of failing, particularly during daytime warming.

Deeper in the snowpack, a persistent weak layer from late January is buried around 80 to 150 cm and is composed of a combination of surface hoar, facets, and crusts. We haven't received a report of avalanche activity on this layer since late February. The likelihood of triggering this layer is low during the current diurnal cycle, with a thick melt-freeze crust expecting to form each night.

As always, best to avoid shallow, rocky areas where a weak and faceted snowpack may be found.

Terrain and Travel

  • Extra caution is needed around cornices under the current conditions.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

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.