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Avalanche Forecast

Archived

Dec 26th, 2024–Dec 27th, 2024

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 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.

Stay diligent with careful terrain selection and good travel habits. Fresh storm slabs in combination with tricky buried weak layers create a complex snowpack.

Confidence

Moderate

Avalanche Summary

On Tuesday, several skier-triggered persistent slabs (size 1) were reported in the Bonnigtons-MIN.

On Thursday, skiers near Rossland remote-triggered storm slabs (size 1-2) on north facing treeline and below treeline terrain. Natural storm slabs up to size 2 were also observed in the area.

Snowpack Summary

15 to 30 cm of new snow has fallen in the past 24 hours. Accompanying southwest winds have redistributed this new snow, forming deeper deposits on leeward slopes at higher elevations.

A crust is present near the surface at lower elevations, with moist snow likely near the valley bottom where precipitation falls as rain.

The upper snowpack continues to settle and bond well following significant snowfall over the last two weeks.

Weak layers of surface hoar or facets and a crust may persist in the mid-snowpack, and snowpack tests continue to indicate potential instability.

The lower snowpack is generally strong and well-bonded.

Weather Summary

Thursday Night

Cloudy with up to 10 cm of new snow. 15 to 40 km/h southwest ridgetop wind. Treeline temperature -5 °C.

Friday

Mostly cloudy with up to 3 cm of new snow. 10 to 30 km/h southwest ridgetop wind. Treeline temperature -6 °C.

Saturday

Cloudy with 5 to 20 cm of new snow. 15 to 40 km/h southwest ridgetop wind. Treeline temperature -3 °C.

Sunday

A mix of sun and cloud with up to 2 cm of new snow. 5 to 15 km/h northeast ridgetop wind. Treeline temperature -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.

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.