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Avalanche Forecast

Archived

Apr 10th, 2021–Apr 11th, 2021

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

Regions

South Coast.

Stay tuned in to hazards lingering from the storm as you keep up the winter stoke. Wind slabs perched in steep leeward pockets, looming cornices, and fresh snow seeing its first sun exposure will all need to be managed on Sunday.

Confidence

High -

Weather Forecast

Saturday night: Clearing. Moderate northwest winds easing to light by morning.

Sunday: Sunny. Light north winds. Alpine high temperature near -2 with freezing levels to 1300 metres, continuing to rise overnight.

Monday: Sunny. Light to moderate northeast winds. Alpine high temperatures around +1 with freezing levels to 1700 metres, remaining elevated overnight.

Tuesday: Sunny. Light to moderate northeast winds. Alpine high temperatures around +3 with freezing levels to 2000 metres.

Avalanche Summary

Early observations from Friday's storm showed touchy new storm slabs set up by the end of the day. This MIN report gives a good idea of the situation. Snowfall continued through the overnight period and although the bond of the new snow may have improved slightly by Saturday, the added load and the addition of solar exposure likely kept conditions quite reactive during the day.

Looking forward to Sunday, solar aspects may continue to shed loose snow with daytime warming and more wind loaded features will likely remain reactive to human triggering as well, even if a bit more stubborn.

Snowpack Summary

30-40 cm of new snow, tapering with elevation, accumulated through Friday night with moderate to strong southwest winds. This new snow is likely to establish a good bond with the old surface by Sunday, however steep wind loaded areas should remain suspect a bit longer.

The new snow and 10-15 more cm of older storm snow from last weekend sits on another crust on sun-exposed aspects, and on all aspects below about 1400 m. This older interface consists of a mix of dry wind affected or soft snow (depending on aspect) above 1400 m. This older snow layer did not seem to be getting involved in Friday's avalanche activity.

Cornices are large and looming along ridgelines and formed fragile new growth during Friday's storm. Their release is unpredictable, requiring a large berth if you're travelling above or below them.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Loose avalanches may start small but they can grow and push you into dangerous terrain.
  • 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.

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.

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.