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Avalanche Forecast

Archived

Jan 3rd, 2020–Jan 4th, 2020

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

Regions

Sea To Sky.

Stormy conditions continue this weekend. Both natural and human-triggered avalanches are very likely, with the potential for very large avalanches to reach the valley bottom. Travel in avalanche terrain is not recommended, including travel in runout zones.

Confidence

High -

Weather Forecast

FRIDAY NIGHT: Cloudy with snowfall, accumulation 30 to 50 cm, moderate southwest wind, alpine temperature -5 C, freezing level 1500 m dropping to 500 m by the morning.

SATURDAY: Cloudy with snowfall, accumulation 10 to 20 cm, moderate to strong southwest wind, alpine temperature -10 C, freezing level 700 m.

SUNDAY: Cloudy with snowfall, accumulation 20 to 40 cm, moderate southwest wind, alpine temperature -7 C, freezing level 800 m.

MONDAY: Cloudy with snowfall, accumulation 10 to 20 cm, moderate southwest wind, alpine temperature -7 C, freezing level 800 m.

Avalanche Summary

On Friday, persistent slab avalanches released to ground in below treeline elevations, on the weak and sugary faceted grains described in the snowpack summary.

On Thursday, many large storm and persistent slab avalanches were triggered by explosives and naturally. Cornices were also reactive to explosives.

These types of avalanches are expected to occur this weekend as the storm continues.

Snowpack Summary

Intense snowfall continues in the region, forming dangerous avalanche conditions. Storm slab avalanches around 30 to 60 cm thick are widespread and they may overly a touchy weak layer of surface hoar. Thicker slabs will be found near ridges at higher elevations, as the snow is falling with strong southwest wind.

Near the bottom of the snowpack around 150 to 200 cm deep, sugary faceted grains and a hard melt-freeze crust exist from mid-November, which is an indicative snowpack setup for large and destructive avalanches. The likelihood of natural and human-triggered avalanches on this layer remains elevated with the rapid loading occurring during this stormy period.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Avoid the runout zones of avalanche paths. Avalanches could run full path.

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.