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Avalanche Forecast

Archived

Jan 13th, 2023–Jan 14th, 2023

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

Continually assess the snowpack for signs of instability with dynamic weather conditions. Another 5-15 cm overnight will further add to the storm slab problem.

Confidence

Moderate

Avalanche Summary

A small (to size 1.5) storm slab avalanche cycle occurred early Friday morning near Kootenay Pass. A number of small storm slab avalanches have occurred over the previous week, failing on a recently buried layer of surface hoar.

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

Snowpack Summary

Upwards of 15 cm forecast for Saturday morning will add to recent storm snow. Expect ongoing surface slab development throughout the day with forecast snow and wind. 20-40 cm of recent snow has buried a layer of surface hoar in wind-sheltered terrain, primarily at the treeline and below.

A melt-freeze crust is buried 60-90 cm. This crust ranges from 2 cm at higher elevations to 10 cm at lower elevations. Below the crust, the mid-snowpack is settled and consolidated. A weak layer of facets and a crust near the bottom of the snowpack continue to be a concern. Treeline snow depths average 160-220 cm.

Weather Summary

Friday night

Snowfall with dropping temperatures, 5-15 cm overnight. Moderate to light south ridgetop winds. Treeline temperature below 0 C. Freezing level falling to 1500 m.

Saturday

Snowfall tapering through the day, localized 24-hr accumulations by Saturday at 4 pm up to 20 cm. Light south ridgetop winds. Treeline high temperature -1 C. Freezing level 1600 m.

Sunday

Snowfall increases through the day, 10 cm during the day followed by 10 cm overnight. Light to moderate south ridgetop winds. Treeline high temperature +1 C. Freezing level 1400 m.

Monday

Cloudy with isolated flurries. Light southwest ridgetop winds. Treeline high temperatures -3 C, freezing level below 1100 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for fresh storm slabs building throughout the day.
  • 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.