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Avalanche Forecast

Archived

Mar 27th, 2025–Mar 28th, 2025

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
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, Retallack, Valhalla, Whatshan.

There is uncertainty with the speed of recovery of the snowpack. Maintain conservative terrain choices while we transition to a cooler weather pattern.

Confidence

Low

Avalanche Summary

A widespread large natural avalanche cycle of wet loose to size 2.5, and persistent slabs up to size 4. While activity peaked on Wednesday, similar avalanche activity is expected to continue with forecasted precipitation and fluctuating freezing levels.

Read the Forecaster Blog for an opportunity to reflect on this week's widespread avalanche activity.

Snowpack Summary

Mixed precipitation will further saturate the upper snowpack at lower elevations. Convective flurries across the region could accumulate 15 to 20 cm of storm snow, which will bury variable surfaces of a melt-freeze crust or moist snow depending on freezing levels.

Several weak layers in the snowpack remain a concern for triggering:

  • Facets/surface hoar/crust from early March buried 50 to 80 cm deep,

  • Facets/surface hoar/crust from mid-February buried 110 to 130 cm deep, and

  • Facets/surface hoar/crust from late January buried 120 to 160 cm deep.

Weather Summary

Thursday Night

Partly cloudy, mixed rain and snow, 3 to 5 cm. 20 to 30 km/h south ridgetop wind. Treeline temperature 0 °C. Freezing level 1800 m

Friday

Cloudy, wet flurries, 10 to 15 cm. 20 to 40 km/h southwest ridgetop wind. Treeline temperature -1 °C. Freezing level 1700 m.

Saturday

Partly cloudy, isolated flurries 5 to 7 cm. 20 to 30 km/h southwest ridgetop wind. Treeline temperature -1 °C. Freezing level 1700 m.

Sunday

Partly cloudy, isolated flurries 1 cm. 15 to 20 km/h variable wind. Treeline temperatures -2 °C. Freezing level 2000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • In times of uncertainty, conservative terrain choices are our best defense.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Keep in mind that human triggering may persist as natural avalanches taper off.

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.

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.

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.