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Avalanche Forecast

Archived

Mar 24th, 2021–Mar 25th, 2021

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

Recently formed slabs are likely bonding but could still be triggered by riders, particularly in steep terrain. Use caution around cornices and on sun-exposed slopes during the heat of the day.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

WEDNESDAY NIGHT: Clearing, 20 km/h north wind, freezing level 1000 m with treeline temperatures around -1 C.

THURSDAY: Sunny skies with periodic clouds, light northeast wind, freezing level climbing to 1500 m with treeline temperatures near 1 C.

FRIDAY: Mostly cloudy, light northwest wind, freezing level around 1000 m with treeline temperatures -1 C. 

SATURDAY: Cloudy, moderate southwest wind, freezing level rising to 1500 m with treeline temperature near 1 C.

Avalanche Summary

On Wednesday, riders triggered loose dry avalanches, which switched to loose wet as the freezing level rose over the day. The avalanches were reported as small (size 1). On Tuesday, this MIN describes recent slab avalanche activity near Mt Strachan. On Monday there were some reports of size 1.5-2 human triggered avalanches in the Seymour backcountry (30-60 cm thick). See the photos here and here. Additionally there were reports of several size 1.5 explosives triggered storm slab avalanches.

Looking forward, storm and wind slabs may remain triggerable at higher elevations and use caution on sun-exposed slopes if clear skies prevail.

Snowpack Summary

10 to 15 cm of snow accumulated on Tuesday night, forming new storm slabs and wind slabs in exposed terrain. This snow overlies 35 to 45 cm of snow from Sunday, which is likely now settled and bonded to the snowpack. The snow surface may moisten on Thursday during periods of sunny skies and with a freezing level rise to 1500 m. Along ridgelines, cornices are large and always have the potential of failing or being triggered from the weight of a human.

Terrain and Travel

  • The new snow may require another day to settle and stabilize.
  • Be careful as you transition into wind affected terrain.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.