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Avalanche Forecast

Archived

Dec 24th, 2022–Dec 25th, 2022

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

Regions

Northwest Coastal, Kitimat, Nass, Rupert, Seven Sisters, Shames, Stewart, Howson.

Ongoing stormy weather with a warming trend is creating dangerous avalanche conditions for Sunday. The storm snow sits over a widespread weak layer which is increasing the reactivity of the new storm slabs.

Confidence

Moderate

Avalanche Summary

An early report on Saturday from the north of the region included a natural size 1.5 storm slab that had occurred overnight and a size 1.5 storm slab that was remotely triggered from 7 m away and was 30 cm thick. Around Bear Pass, a few natural wind slabs up to size 2 were observed.

This MIN report from Friday shows a small wind slab avalanche with a relatively wide propagation given the thin slab and suggests a poor bond between the new snow and the old surface. Also on Friday in the south of the region, a natural size 1 wind slab was reported on a SW aspect. A skier-triggered size 1 slab was also reported which was only 10 cm thick but had failed on a weak layer of facets. With ongoing snowfall, these types of avalanches are expected to continue and will likely increase in size and reactivity.

Snowpack Summary

The new storm snow has buried a highly variable snow surface that had formed during the recent period of extended cold temperatures and outflow winds. This newly buried weak layer consists of widespread facets, patchy surface hoar in sheltered terrain, and heavily wind-affected surfaces in exposed terrain including wind-scoured and wind-pressed surfaces, old hard wind slabs, and sastrugi.

A layer of large surface hoar crystals, buried in early December, was found down 20 to 50 cm prior to the storm. This layer has previously produced small but remotely-triggered avalanches.

The lower snowpack is well consolidated above a crust that had formed in mid-November which can be found below around 1200 m elevation.

Weather Summary

A series of storm systems will continue to impact the region. A warming trend is expected for Sunday with freezing levels climbing to around 1500 m elevation.

Saturday night

Snowfall 20-40 cm, strong to extreme SW wind, treeline low around -8 °C, rising by early morning.

Sunday

Snowfall 10-20 cm, strong SW wind, treeline high around 0 °C with a chance of a temperature inversion.

Sunday night and Monday

Snowfall 20-30 cm, moderate to strong S-SW wind, treeline high around 0 °C with a chance of a temperature inversion.

Tuesday

Mainly cloudy with a chance of sunny breaks, moderate to strong NE wind, treeline high around -4 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Watch for changing conditions today, storm slabs may become increasingly reactive.
  • Extra caution for areas experiencing rapidly warming temperatures for the first time.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger 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.

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.