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Avalanche Forecast

Archived

Jan 13th, 2022–Jan 14th, 2022

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

Regions

South Columbia.

Hazard will likely depend on the extent of cooling and new crust formation Thursday night. Storm slabs are expected to remain touchy up high where the snow remains dry, especially in wind loaded terrain. Use extra caution around steep south facing slopes if the sun is strong.

Confidence

Moderate - Uncertainty is due to rapidly fluctuating freezing levels.

Weather Forecast

A ridge of high pressure brings dry and partly sunny conditions for Friday before a weak storm system arrives Friday night. 

Thursday night: Partly cloudy, light variable wind, freezing levels dropping to around 500 m. 

Friday: A mix of sun and cloud, light SW wind, freezing levels reaching as high as 1500 m. 

Saturday: Snowfall up to 20 cm, moderate SW wind, freezing levels reaching around 1300 m.

Sunday: Periods of light snowfall, light to moderate SW wind, freezing level reaching around 800 m.

Avalanche Summary

On Wednesday, natural storm slabs up to size 2.5 typically releasing down 20-40 cm, some of which were failing on a layer of surface hoar. Natural loose dry avalanches were being reported in extreme terrain at higher elevations and one loose wet avalanche was triggered at lower elevation. Humans and explosives were also triggering a variety of avalanches in the storm snow. On Tuesday, a variety of natural and human triggered avalanches up to size 2.5 were observed. 

The persistent early December crust/facet layer has recently been active in this region. Concern for persistent slab activity like this is being sustained by new snow, wind, and warming. On Monday, a few very large simultaneous remote triggered persistent slab avalanches were reported in this Mountain Information Network (MIN) report south of Kaslo. It reported as a near miss, triggered from 150 m away on northeast through southeast features around treeline. The crown was one meter deep and propagated 500 m wide. On Friday, three naturally triggered size 2-3 avalanches on this layer were reported in mountain ranges just west of the Columbia river. They were reported at treeline and above on south and east aspects. Some were known to be wind slab avalanches that stepped down to this deeper, persistent layer in a thin, rocky area. 

Snowpack Summary

On Thursday, freezing levels climbed to at least treeline. With temperatures expected to drop on Thursday night, a widespread surface crust is expected to form. Below the new crust, 30-60 cm of recent storm snow is settling rapidly with the mild temperatures. This recent storm snow overlies the January 10 interface which may include weak facets and/or surface hoar. Another layer of facets from early January can be found down 60-90 cm.

We're still actively monitoring the early December crust. In some places, it's down 80 cm, while in wind-loaded terrain features it can be found as deep as 200 cm below the surface. It consists of faceted grains above a bulletproof crust formed by the Atmospheric Rivers of early December. There has been avalanche activity on this crust over the weekend. Larger avalanches in surface layers as well as natural cornice falls may still have potential to step down to this layer.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.
  • Avoid exposure to steep sun exposed slopes.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.