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Avalanche Forecast

Archived

Mar 10th, 2024–Mar 11th, 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

Lizard-Flathead, South Rockies, Akamina, Flathead, Lizard, Bull, Crowsnest North, Crowsnest South, Elkford East, Elkford West.

Human triggering of persistent slab avalanches continues to be reported.

Expect to find fresh wind slabs at higher elevations, but buried weak layers remain the primary concern.

Confidence

Moderate

Avalanche Summary

A large human triggered persistent slab was reported on Saturday from a steep alpine slope. Cornice falls were also reported to be triggering slab avalanches on the slope below.

Previous in the week, large to very large slab avalanches were triggered naturally and by explosives, size 2 to 3.5. Primary concern is for further activity on these buried weak layers, producing large avalanches.

Snowpack Summary

Up to 20 cm of snow is expected by Monday afternoon, accumulating over a crust on sun affected slopes, surface hoar in sheltered terrain, and wind affected snow in exposed areas. Storm snow is not expected to bond well with the old snow surfaces below.

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

Sunday Night

Cloudy with up to 15 cm of snow expected. 30-50 km/h southwest winds. Freezing levels remain around 1200 m.

Monday

Cloudy with another 5 cm possible. 40-60 km/h southwest ridgetop wind. Treeline temperature -4 °C. Freezing level 1500 m.

Tuesday

Cloudy with up to 10 cm of snow. 30-40 km/h southwest ridgetop wind. Treeline temperature -4 °C. Freezing level 1500 m.

Wednesday

A mix of sun and cloud with isolated flurries. 10-20 km/h southwest ridgetop wind. Treeline temperature -3 °C. Freezing level 1600 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Conservative terrain selection is critical, choose only well supported, low consequence lines.
  • Remote triggering is a concern, watch out for adjacent and overhead slopes.
  • Cornice failures could trigger very large and destructive avalanches.

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.