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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 Inland.

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. Light northwest winds.

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

Monday: Mainly sunny. Light northeast winds. Aline high temperatures around -3 with freezing levels to 1700 metres.

Tuesday: Sunny. Light to moderate northeast winds. Alpine high temperatures around 0 with freezing levels to 2000 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 slippery crust lower down, and natural loose wet activity where sun poked out to destabilize surface snow. This mix of hazards was almost certainly more pronounced in the south of the region, which saw 2-3 times 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 cm of new snow fell in the north of the region through Friday night, closer to 20-30 cm near the Coquihalla, with amounts tapering off with elevation. Moderate to strong southwest winds accompanied this snowfall, moving snow into thicker, more reactive slabs in leeward terrain features. The new snow adds to 10-20 cm that fell last weekend. 

Collectively, this new and recent snow sits on a crust in most areas, except on north aspects above about 1500 m where it sits on older wind slabs or soft snow, depending on wind exposure.

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.