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

Regions

North 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: Mainly cloudy, light variable wind, freezing levels dropping to around 500 m. 

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

Friday night and Saturday: Snowfall up to 25 cm, moderate to strong SW wind, freezing levels reaching around 1300 m.

Sunday: Snowfall, light to moderate SW wind, freezing level reaching around 800 m.

Avalanche Summary

On Wednesday, natural avalanches up to size 3 were reported and natural dry loose avalanches up to size 2 were observed in extreme terrain. Several natural size 1 storm slabs were also reported failing down 15-20 cm as well as size 1 wet loose avalanches from steep below-treeline terrain. Skiers and explosives were also triggering a variety of avalanches. On Tuesday, a variety of natural avalanches up to size 3 were observed. 

The early-December persistent crust/facet layer has been active in this region as recently as Sunday, producing avalanches up to size 3. This layer is still a concern in the region but the likelihood of an avalanche on this layer continues to decrease as temperatures drop following the warming event. 

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, 40-60 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 shallow spots it's down 90 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

  • Choose conservative terrain and watch for clues of instability.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
  • Avoid areas with overhead hazard.

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.