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Avalanche Forecast

Archived

Mar 21st, 2025–Mar 22nd, 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 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.

15 to 25 cm of recent snow and southwest wind have formed fresh storm slabs.

Expect strong solar radiation to increase the likelihood of triggering slabs.

Confidence

Moderate

Avalanche Summary

On Thursday, numerous skier triggered storm slabs up to size 1.5 and one size 2 persistent slab were reported. They occurred primarily on northerly and easterly aspects. Here's one example.

Additionally, a naturally triggered size 3 persistent slab was reported on northeast aspect in the alpine. It was likely triggered by either rapid loading or a cornice fall.

Snowpack Summary

15 to 25 cm of recent snow and southwest wind have formed 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

Friday night

Cloudy with 0 to 10 cm of snow (isolated areas could receive up to 20 cm). 10 to 20 km/h west ridgetop winds. Treeline temperature -8 °C. Freezing level valley bottom.

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 southwest ridgetop winds. Treeline temperature -4 °C. Freezing level 1400 m.

Monday

Moslty cloudy with 0 to 5 cm of snow. 20 to 30 km/h southwest ridgetop winds. Treeline temperature 2 °C. Freezing level rapidly rising to 2200 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.
  • 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.
  • Even brief periods of direct sun could produce natural avalanches.

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.

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.