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 4th, 2020–Jan 5th, 2020

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 and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Kootenay Boundary.

The snowpack likely needs more time to stabilize, especially where recent snow overlies weak layers. There is also still concern for triggering deeper weak layers. Conservative decision-making is essential to manage these avalanche problems.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

SATURDAY NIGHT: Partly cloudy, moderate west wind, alpine temperature -9 C, freezing level 500 m.

SUNDAY: Mostly cloudy with afternoon snowfall, accumulation 2 to 5 cm, moderate southwest wind, alpine temperature -7 C, freezing level 800 m.

MONDAY: Mix of sun and cloud with afternoon snowfall, accumulation 2 to 5 cm, moderate west wind, alpine temperature -9 C, freezing level 500 m.

TUESDAY: Cloudy with snowfall, accumulation 15 to 25 cm, moderate to strong southwest wind, alpine temperature -3 C, freezing level 1100 m.

Avalanche Summary

Small avalanches were observed in the most recent storm snow on Friday.

On Thursday, many large storm slab avalanches were reported, being triggered naturally and by humans. They were generally 20 to 50 cm deep and occurred at treeline and alpine elevations. Further, two large avalanches occurred on the deeply buried weak layers described in the snowpack summary, suggesting that they are still problematic layers.

Snowpack Summary

Around 40 to 60 cm of recent storm snow has formed touchy storm slabs. The snow has been redistributed by strong southwest wind, making the slabs thicker and more reactive in lee features near ridges. These slabs have been capped with a thin layer of ice at all elevations in many parts of the region, which may limit further wind transportation. The storm snow may overly a weak layer of feathery surface hoar and a hard melt-freeze crust on sun-exposed aspects, which has increased the reactivity of these slabs.

There are multiple weak layers buried around 80 to 120 cm deep, including two more surface hoar layers and weak faceted snow near the bottom of of the snowpack. This fundamentally unstable snowpack structure remains a concern, as it is capable of producing large and destructive avalanches. It is possible that storm slab avalanches could step down to these deeper layers or the layers could be triggered in areas where the snowpack is relatively thin.

Terrain and Travel

  • Make conservative terrain choices and avoid overhead hazard.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.