Avalanche Forecast

Archived

Mar 17th, 2025–Mar 18th, 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 unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

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, Kokanee, Retallack, Valhalla, Whatshan.

Up to 60 cm of recent snow has formed reactive storm slabs.

These slabs will be most reactive on wind-loaded slopes and on sunny slopes during periods of strong solar radiation.

Confidence

Moderate

Avalanche Summary

On Sunday, numerous naturally triggered storm slab avalanches up to size 2 were reported primarily at treeline and above on a variety of aspects.

Additionally, a snowcat triggered a persistent slab avalanche on the early March Surface hoar layer on a north aspect at treeline.

Numerous explosive triggered storm slab avalanches were reported primarily at treeline on a variety of aspects.

Snowpack Summary

40 to 60 cm of recent snow and southwest winds formed 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

Monday Night

Mostly clear, 10 to 20 km/h northwest ridgetop winds, treeline temperature -8 °C, freezing level valley bottom.

Tuesday

Sunny, 10 to 20 km/h northwest ridgetop winds, treeline temperature -5 °C, freezing level 1400 m.

Wednesday

Mix of sun and cloud, 20 to 30 km/h southwest ridgetop winds, treeline temperature -5 °C, freezing level 1500 m.

Thursday

Cloudy with flurries, 5-10 cm snow, 20 to 30 km/h southwest ridgetop winds, treeline temperature -4 °C, freezing level 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Remote triggering is a concern; avoid terrain where triggering overhead slopes is possible.
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.
Avoid steep, sun-exposed slopes when the air temperature is warm or when solar radiation is strong.

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.