Avalanche Forecast

Archived

Feb 25th, 2025–Feb 26th, 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.

Strong sunshine may trigger natural avalanches, and storm snow likely remains reactive to human triggers.

Don't let sun and clear skies tempt you into consequential terrain.

Confidence

Moderate

Avalanche Summary

On Monday, avalanche activity reached size 3.5, with natural avalanches occurring during heavy snowfall and strong winds. Avalanches were triggered within the storm snow and on buried weak layers.

Several avalanches were remotely triggered (from a distance) or sympathetically by other avalanches, clear signs of instability.

While natural activity is expected to taper off, human triggering remains a concern.

Snowpack Summary

Recent snowfall has settled to around 30 to 50 cm of new snow, with wind effect observed at higher elevations. Strong sunshine on Wednesday is expected to create moist snow on sun-exposed slopes and moist snow is also present at lower elevations due to recent warm temperatures and rain.

Two key weak layers are present in the mid snowpack: a surface hoar or thin crust from mid-February buried 40-60 cm deep, and faceted snow/surface hoar/crust from late January buried 60-100 cm deep.

These weak layers are expected to remain reactive from the heavy snowfall and warm temperatures. The remainder of the snowpack is generally well-settled.

Weather Summary

Tuesday Night

Cloudy with flurries tapering off early evening. 10 to 20 km/h west ridgetop wind. Freezing level drops to 500 m.

Wednesday

Mostly clear skies with morning cloud. 20 to 30 km/h southerly ridgetop winds. Treeline temperature -3 °C. Freezing level rising to 1700 m.

Thursday

Mostly clear skies. 40 to 50 km/h southwest ridgetop winds. Treeline temperature +1 °C. Freezing level rising to 2000 m.

Friday

Clear skies. 20 to 30 km/h southwest ridgetop winds. Treeline temperature +5 °C. Freezing level rising to 2500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Even brief periods of direct sun could produce natural avalanches.
Travel early on sun-exposed slopes before cornices weaken with daytime warming.

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.