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Avalanche Forecast

Archived

Apr 11th, 2021–Apr 12th, 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.
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.

Tune in and anticipate the effects of warming as you travel. It will affect increasingly high elevations and shaded aspects over the coming days. Be especially wary of slopes with cornices above them.

Confidence

High -

Weather Forecast

Sunday night: Mainly clear. Light northeast winds increasing into the morning.

Monday: Sunny. Light to moderate northeast winds. Alpine high temperatures around -4 with freezing levels to 1600 metres.

Tuesday: Sunny. Light to moderate northeast winds, increasing over the day and overnight. Alpine high temperatures around 0 with freezing levels to 2100 metres.

Wednesday: Sunny. Moderate northeast winds. Alpine high temperatures around +4 with freezing levels to 2500 metres.

Avalanche Summary

Saturday's MIN was active! Several users in the region and many more in the neighbouring Sea to Sky and South Coast proper encountered unstable snow conditions. Avalanche activity appears to have been limited to the depth of our latest storm snow.

Looking forward, Monday's concerns should be limited to lingering wind slabs and predictable wet loose activity connected to daytime warming. Tuesday ushers in the start of a dramatic warming trend that will likely expand the extent of wet loose concerns to higher elevation, more shaded aspects and may eventually test deeper snowpack layers.

Snowpack Summary

New surface melt-freeze crusts formed on many solar aspects by the end of the day Saturday atop 10-20 cm of new snow that fell in the north of the region through Friday night, closer to 20-30 cm near the Coquihalla (amounts taper off with elevation). Moderate to strong southwest winds accompanied the snowfall, followed by a lighter northwest flow, leaving behind varying levels of wind effect on many aspects in open terrain.

For the most part the new snow buried (and was reactive over) recent solar and temperature crusts, but it may have added to dry settled snow on higher shaded aspects.

Solar warming will break down surface crusts and encourage wet loose releases -both natural and human triggered- each day on solar aspects and increasingly toward shaded alpine terrain as freezing levels march upward over the coming days.

Cornices are large and looming along ridgelines and they formed fragile new growth during the storm. Their release is unpredictable but increases in likelihood with daytime warming, requiring a large berth if you're travelling above or below them.

Terrain and Travel

  • 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.
  • Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.

Problems

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.

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.