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Avalanche Forecast

Archived

Feb 5th, 2022–Feb 6th, 2022

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

Regions

North Columbia.

The recent snow loaded a buried weak layer. There is uncertainty on where exactly this layer may be buried and how the recent snow will affect it. Rising temperatures and sun on Sunday increase the likelihood for riders to trigger avalanches. Give the snowpack time to stabilize.

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

SATURDAY NIGHT: Clear with increasing clouds, trace of new snow, light to moderate west wind, alpine temperature -4 C, freezing level 600 m. 

SUNDAY: Cloudy in the morning and clear in the afternoon, trace of new snow, light to moderate southwest wind, alpine temperature 0 C, freezing level rising to 2000 m.

MONDAY: Cloudy with snowfall, 5 to 10 cm new snow, moderate to strong west wind, alpine temperature -4 C, freezing level 1500 m.

TUESDAY: Cloudy, up to 3 cm new snow, light to moderate southwest wind, alpine temperature -5 C, freezing level 1300 m. 

Avalanche Summary

Observations on Friday were limited due to visibility. A natural avalanche cycle of small slabs up to size 1.5 was observed, as well as a few large (size 2.5 to 3) storm slab avalanches on northeast and south aspects at treeline. Skiers triggered small storm/wind slab avalanches, and explosives triggered numerous large (up to size 2.5) avalanches. 

A handful more storm and wind slabs were triggered by riders on Thursday to add to the many avalanches observed in the previous few days. Most of the storm slabs released on the surface hoar layer described in the Snowpack Summary, often occurring between around 1700 and 2200 m on east, north, and west aspects. Check out some good example photos here. 

Large avalanches are still expected to be easily triggered by riders on Sunday in areas where the buried surface hoar described in the Snowpack Summary exists. Avoidance of avalanche terrain, particularly where the surface hoar may exist, is your best bet for having a safe day.

Snowpack Summary

The recent storm brought 20 to 40 cm with locally higher amounts. The snow has formed new storm slabs in areas sheltered from the wind and wind slabs in exposed terrain at higher elevations from strong south to southwest wind. 

The snow loaded a weak layer of surface hoar crystals 5 to 15 mm in size. Forecast warming may also increase the likelihood of triggering a slab. The layer may be around 60 to 100 cm deep, which is a prime depth for human triggering. The layer is most prominent in areas sheltered from the wind. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns. The layer may not exist on steep sun-exposed slopes, where a melt-freeze crust may be found instead.

The facet/crust layer that formed in early December is buried around 120 to 250 cm. The last reported avalanche was on January 31 from a large explosive, and before that on January 23. Although unlikely, the layer could be triggered from a large load like a cornice fall or a shallower slab avalanche could step down to this layer. Humans are unlikely to trigger it, with perhaps the exception in thin, shallow snowpack areas. Check out the forecaster blog for more information.

Terrain and Travel

  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
  • Avoid steep slopes when air temperatures are warm, or solar radiation is strong.

Problems

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.

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.

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.