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Avalanche Forecast

Archived

Mar 24th, 2022–Mar 25th, 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

Kootenay Boundary.

Be thoughtful with your terrain choices, and pay attention to how the weather is affecting the snowpack through the day. Uncertainty about a buried persistent weak layer would make me hesitant to ride a big, committing feature.

Confidence

Moderate - The snowpack structure is generally well understood. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

THURSDAY NIGHT: Partly cloudy. No new precipitation expected. Light southeast ridgetop wind. Freezing level around 1750 m. 

FRIDAY: Partly cloudy. No new snow expected. Light southwest ridgetop winds. Freezing level rising to around 2100 m.

SATURDAY: Partly cloudy. No new snow expected. Light south ridgetop wind. Freezing level around 2200 m. 

SUNDAY: Mostly cloudy. Light rain overnight, possible snow at high elevations. Light to moderate southwest ridgetop wind. Freezing level rising to 2500 m. 

Avalanche Summary

On Tuesday and Wednesday, widespread, loose wet avalanches were reported due to warm temperatures and/or sunshine (size 1-2). 

There have been some notable human-triggered avalanches in Kootenay Pass and the Nelson area in the past week. These large slab avalanches (size 2), failed on either a buried sun crust on solar aspects or surface hoar on shaded aspects. On Wednesday, south of Nelson, a large, naturally triggered avalanche was reported that may have failed on or stepped down to this layer. It started on an east through southeast aspect just above treeline.

Snowpack Summary

A skiff of new snow and possibly thin windslabs in the high alpine. Refrozen crust on all aspects up to 2200 m, softening in the afternoon at low elevations and on steep, sunny slopes. Recent warm temperatures, sun, and rain have made the top 10-30 cm of the snowpack moist. Below 1500 m, the snowpack may be wet and isothermal if the freezing levels don't drop enough overnight. 

40 to 70 cm below the snow surface, you'll find a frozen sun crust on solar aspects, and weak, feathery surface hoar crystals on shaded aspects. This layer was buried in early March. During the last storm, it produced surprising avalanches in certain areas of the Selkirks (east side of the region). The recent warm weather seems to have helped this layer heal, but it's not yet time to take it out of your danger assessment for the day.

The mid and lower snowpack are generally strong and well bonded.

Terrain and Travel

  • If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Be alert to conditions that change with aspect and elevation.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.