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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

Sea To Sky.

Stay tuned in to hazards lingering from the storm. 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. Greater new snow accumulations mean greater hazard in the south of the region.

Confidence

High -

Weather Forecast

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

Sunday: Mainly sunny. Light north winds. Alpine high temperatures around -6 with freezing levels to 1400 metres.

Monday: Sunny. Light northeast winds. Alpine high temperatures around -3 with freezing levels to 1700 metres.

Tuesday: Sunny. Light northeast winds. Alpine high temperatures around 0 with freezing levels to 2100 metres.

Avalanche Summary

We don't yet have reports showing the results of Friday's storm, but it's likely that surface instabilities were quite active on Saturday, with a mix of wind slab hazards in higher elevation, wind exposed terrain, potentially storm slabs over a slippery crust lower down, and natural loose wet activity on steep slopes where sun exposure destabilized the surface. This mix of hazards was almost certainly more pronounced in the south of the region, which saw up to triple the accumulations of the north.

Looking forward, the new snow is likely to form a reasonable bond with the old surface by Sunday, however recently wind loaded areas and slopes that see solar warming should remain suspect over the near term.

Snowpack Summary

About 10-30 cm of new snow, with a strong southern focus, accumulated through Friday night with strong to extreme south and east winds. Whistler Peak saw gusts of up to 140 km/h. The new snow brings storm totals from this week to about 25-50 cm. Collectively, this recent snow sits on a crust on sun-exposed aspects, and on all aspects below about 1600 m. It likely sits on soft snow or on older wind slabs on north aspects. 

Cornices are large and looming along ridgelines and they formed fragile new growth during the 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.