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Avalanche Forecast

Archived

Apr 22nd, 2021–Apr 23rd, 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 possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Kootenay Boundary.

Change is in the air, but even short periods of sunshine combined with high freezing levels can pack a punch. Loose wet avalanches are possible on sun-exposed slopes in the afternoon. 

Steer clear of cornices from above and below.

Confidence

Moderate - The snowpack structure is mostly striaghtforward and not unusually variable. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Overnight Thursday: Clear with a light East wind. Alpine temperatures near -5 and freezing levels 800 m. 

Friday: A mix of sun and cloud. Ridgetop wind light to moderate from the southeast. Alpine temperatures near +2 and freezing levels 2000 m.

Saturday: Precipitation 15-25 mm falling as snow in the alpine and rain below. Ridgetop wind moderate from the southeast. Alpine temperatures near 0 and freezing levels 2000 m.

Sunday: Snow 5-10 cm. Ridgetop wind strong from the southwest. Alpine temperatures near -3 and freezing levels 1700 m. 

 

Avalanche Summary

There have been no recent avalanche reports since last Saturday. 

Last weekend, reports of natural loose wet avalanches size 2-3 on solar aspects continued. Explosive work produced size 2-3.5 wet slab avalanches, failing on crusts in the upper snowpack and gouging to the ground as they ran to near valley bottom.

As the weather pattern changes and the temperatures start to fall, a decline in natural avalanche activity is likely. However, solar slopes and weak cornices remain suspect when the sun is shining. It can really pack a punch this time of year, even for short periods of time. 

Snowpack Summary

The snow surface consists of a melt-freeze crust on all aspects of the mountain top. Only high alpine slopes above 2100 m and due North may still hold some softer, dryer snow. With a limited freeze overnight and rising freezing levels by Thursday afternoon, this crust may break down quickly with mostly wet snow surfaces. There are no layers of concern in the snowpack, which has been melting and settling over the past week. Lower elevations have mostly been isothermal and melting away rapidly.

Large cornices loom along many ridgelines. They are weak and very unpredictable.

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Terrain and Travel

  • Avalanche hazard is expected to to increase througout the day, think carefully about your egress.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

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.