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Avalanche Forecast

Archived

Mar 9th, 2024–Mar 10th, 2024

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

Regions

Kootenay Boundary, Bonnington, Grohman, Kootenay Pass, Norns, Rossland, Ymir, Crawford, Moyie, St. Mary, Kokanee, Valhalla.

Expect to find fresh wind slabs at higher elevations, but buried weak layers remain the primary concern. The potential for large and destructive avalanches continues.

Confidence

Moderate

Avalanche Summary

Last reported avalanches are from explosive control work on Thursday, producing slabs up to size 4.

Recent avalanches have been large and destructive, running full path. Check out the photos below for an explosive triggered avalanche near Nelson, and a rider triggered avalanche in the Bonningtons on Tuesday. While natural activity appears to have tapered off, human triggering is still a concern and will likely produce a high consequence avalanche.

Snowpack Summary

Storm totals are expected to reach 10-30 cm by Sunday afternoon, falling on a variety of weak surfaces - a crust on sun affected slopes, surface hoar in sheltered terrain, and wind affected snow in exposed areas.

A widespread crust with weak facets above remains a concerning layer for human triggering. Buried 80-150 cm deep, this layer has produced very large avalanche activity this week.

The snowpack below the crust is generally strong.

Weather Summary

Saturday Night

Cloudy with 5-10 cm of snow. 30-50 km/h southwest ridgetop wind. Freezing levels drop to around 1000 m.

Sunday

Cloudy with 5 to 15 cm of snow. 40 km/h southwest ridgetop wind, gusting to 80 km/h. Freezing levels rise to 1500 m, with treeline temperatures around -3 °C.

Monday

Cloudy with 5 cm of snow. 20-30 km/h southwest ridgetop wind. Freezing levels rise to 1500 m, with treeline temperatures around -3 °C.

Tuesday

Cloudy with 5-15 cm of snow. 30-50 km/h southwest ridgetop wind. Freezing levels rise to 1500 m, with treeline temperatures around -3 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Remote triggering is a concern, watch out for adjacent and overhead slopes.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

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.

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.