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Avalanche Forecast

Archived

Mar 5th, 2022–Mar 6th, 2022

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast.

Wind slab formation is expected in exposed terrain at higher elevations due to ongoing periods of moderate northerly wind. Use extra caution around cornices and steep south-facing slopes during the heat of the afternoon. 

Confidence

Low - Uncertainty is due to the limited number of field observations. Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

A ridge of high pressure brings one more day of dry and sunny conditions for Sunday before conditions change on Monday. 

Saturday Night: Clear, light to moderate N wind, freezing levels around 1500 m.

Sunday: Sunny, light to moderate N wind, freezing levels climbing to around 2000 m.

Monday: Mainly cloudy with a chance of flurries, strong NW wind, freezing levels around 2000 m in the morning, dropping to around 1000 m in the afternoon.

Monday night and Tuesday: Snowfall up to 15 cm, light to moderate NW wind, freezing levels around 800 m.

Avalanche Summary

On Friday, this MIN report includes numerous size 1 loose wet avalanches on east through south aspects. 

A persistent slab avalanche problem is prevalent just north of the region in the southern Sea to Sky. While there hasn't been any observations of this problem in the South Coast region, it may exist in some of the data sparse parts of the region outside of the North Shore. This blog post goes into further details on the problem. 

Snowpack Summary

A melt-freeze crust is now expected to be capping the snowpack on all aspects at elevations below around 1700 m and on sun-exposed slopes at higher elevations. Dry surface snow may still exist on high elevation northerly aspects. Periods of moderate northerly wind over the weekend may have redistributed this old storm snow in exposed high elevation terrain and formed wind slabs. 

A weak interface from mid-February can be found 30-60 cm deep which may include a sun crust, facets, and/or spotty surface hoar. This interface was bonding poorly at the beginning of the storm but has become less of a problem now where the snowpack is capped by a robust crust. At higher elevations where the snowpack is not capped by a crust, the interface may still be reactive. Check out the Sea to Sky Forecast and this forecaster blog to learn more about the recent reactivity on this layer which is still reactive just north of the region.

50-80 cm below the surface, a 30 cm thick crust caps the underlying snowpack which is well-settled and strong.

Check out the latest North Shore Snowpack video for additional details for that area. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • Cornices become weak with daytime heating or solar exposure.

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.