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Avalanche Forecast

Archived

Mar 20th, 2025–Mar 21st, 2025

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

Regions

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

Forecast snow and wind are expected to form fresh storm slabs reactive to human triggers.

Watch for rapidly changing conditions during periods of heavy loading from new snow and wind.

Confidence

Moderate

Avalanche Summary

On Wednesday, a couple cornice failures triggered persistent slabs up to size 2.5 at treeline and above.

Snowpack Summary

Forecast snow and wind are expected to form fresh storm slabs reactive to human triggers.

Concern remains for triggering persistent slab avalanches. These layers include:

  • Facets/surface hoar/crust from early March buried 40-70 cm.

  • Facets/surface hoar/crust from mid-February buried 60-100 cm

  • Facets/surface hoar/crust from late January buried 100-160 cm.

The lower snowpack is well settled and strong.

Weather Summary

Thursday night

Cloudy with 5 to 15 cm of snow. 20 to 30 km/h south ridgetop winds. Treeline temperature -6 °C. Freezing level 1200 m.

Friday

Cloudy with 10 to 20 cm of snow. 20 to 30 km/h southwest ridgetop winds. Treeline temperature -4 °C. Freezing level 1600 m.

Saturday

Mix of sun and cloud. 10 to 20 km/h west winds. Treeline temperature -4 °C. Freezing level 1500 m.

Sunday

Mostly cloudy with 5 to 15 cm snow. 10 to 20 km/h south ridgetop winds. Treeline temperature -3 °C. Freezing level 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks, or recent avalanches.
  • Watch for rapidly changing conditions during periods of heavy loading from new snow, wind, or rain.
  • Remote triggering is a concern; avoid terrain where triggering overhead slopes is possible.
  • Use small, low consequence slopes to test the bond of the new snow.
  • Be aware of the potential for larger than expected storm slabs due to buried surface hoar.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.