Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Jan 15th, 2023–Jan 16th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Kootenay Boundary, Bonnington, Kootenay Pass, Norns, Rossland, South Okanagan, Ymir.

Continually assess the snowpack for signs of instability. Be especially suspicious of shallow or rocky ridges and start zones.

Confidence

Moderate

Avalanche Summary

A widespread and reactive storm slab was reported around the region Friday and into Saturday. Skiers, vehicles, and explosives triggered slabs to size 2.5 with most crowns 30-50 cm deep, and many reported at treeline elevations 1700-2100 m (note poor visibility and no alpine observations). Most avalanches have been reported failing on the most recent interface or a crust/surface hoar layer about 10 cm lower. Wet, loose avalanches were observed in below tree line terrain.

On Saturday, explosives triggered a large (size 2.5) deep persistent slab avalanche (on the western side of the Forecast region, which has received a bit more storm snow over the weekend). This avalanche continues to indicate that while a large load was applied to this slope, this deep persistent layer is still reactive to triggers.

Please continue to share any observations or photos on the Mountain Information Network.

Snowpack Summary

Flurries continue to accumulate around the region, and another 5-15 mm is forecast overnight Sunday through Monday afternoon.

Weekend precipitation fell as rain at lower elevations with freezing levels exceeding 1900 m. Upper elevation storm snow totals vary from 15-30 cm.

At higher elevations, 20-60 cm of snow over the last week has buried a layer of surface hoar from the start of January in wind-sheltered terrain, primarily around treeline.

A facet/crust layer is down 40-90 cm (and 2-10 cm thick at TL elevation), below the mid-pack below is settled and consolidated.

A concerning and weak layer 20-50 cm facets and crust makes up the basal snowpack. Treeline snow depths average 150-210 cm.

Weather Summary

Sunday night

Cloudy with isolated flurries, up to 5 cm. Light south ridgetop wind. Treeline low temperature below -3 C. Freezing level falling below 1000 m.

Monday

Flurries through the day, up to 10 mm in 24 hours. Light to calm south-southwest ridgetop wind. Treeline high temperature 0 C. Freezing falling below 1200 m.

Tuesday

Mostly cloudy with very isolated flurries. Light to calm northwest ridgetop wind. Treeline high temperature -2 C.

Wednesday

Cloudy with isolated flurries. Increasing south ridgetop wind. Treeline high temperature -4 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Closely monitor how the new snow is bonding to the old surface.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.