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Avalanche Forecast

Archived

Jan 8th, 2020–Jan 9th, 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 unlikely, human triggered possible.
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.

Storm slabs may remain sensitive to human triggering and have the potential to step down to deeper weak layers. It is uncertain how fast the snowpack will recover and gain strength. Assess the snowpack and travel conservatively to safely manage the avalanche problems.

Confidence

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

Weather Forecast

WEDNESDAY NIGHT: Clear sky with some clouds and isolated flurries, light northwest wind, alpine temperature -14 C, freezing level below valley bottom.

THURSDAY: Mix of sun and cloud, light northwest wind, alpine temperature -17 C, freezing level below valley bottom.

FRIDAY: Cloudy with snowfall, accumulation 5 cm, moderate southwest wind, alpine temperature -12 C, freezing level below valley bottom.

SATURDAY: Cloudy with flurries, light southwest wind, alpine temperature -8 C, freezing level at 400 m.

Avalanche Summary

On Wednesday, a few natural storm slab avalanches of size 2 were observed. Several explosive triggered storm slab avalanches of up to size 2 were reported.

A widespread natural avalanche cycle occurred in the region on Tuesday with large storm slab avalanches to size 2.5. Numerous explosive and skier triggered storm slab avalanches up to size 2.5 were reported.

Snowpack Summary

Around 40 to 70 cm of snow fell in the region during the most recent storm, which formed touchy storm slabs. The slabs may be particularly touchy in exposed lee terrain features, as the snow fell with strong southwest wind.

Deeper in the snowpack, a few layers of weak and feathery surface hoar may still be found around 50 to 150 cm deep. It is unclear whether they are still problematic and if so, how long they will be so for. The base of snowpack is also weak in parts of the region, where it consists of sugary faceted snow around a melt-freeze crust. Until these weak layers can be ruled out, best to travel conservatively.

Terrain and Travel

  • Don't let the desire for deep powder pull you into high consequence terrain.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, storm slabs in-motion may step down to deeper layers and result in very 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.