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Avalanche Forecast

Archived

Jan 4th, 2022–Jan 5th, 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 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, human triggered possible.

Regions

Sea To Sky.

It may take some time for all the recent snow to stabilize. Conservative terrain travel is needed.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

TUESDAY NIGHT: Evening snowfall then clearing skies, accumulation 5 cm, 10 to 20 km/h northwest wind, alpine temperature -13 C.

WEDNESDAY: Partly cloudy with no precipitation, 10 to 20 km/h west wind, alpine temperature -12 C.

THURSDAY: Cloudy with snowfall, accumulation 15 to 30 cm, 50 km/h southwest wind, alpine temperature -7 C.

FRIDAY: Cloudy with snowfall then clearing, accumulation 10 cm, 20 km/h west wind, alpine temperature -7 C.

Avalanche Summary

A widespread avalanche cycle was observed within the storm snow on Sunday and Monday. More storm slab avalanches were observed on Tuesday from explosives and riders. The avalanches were generally small to large (size 1 to 2). The likelihood of humans triggering the storm snow remains elevated.

Snowpack Summary

Over 100 cm of snow has accumulated since January 1. The snow has formed touchy storm slabs in sheltered terrain and wind slabs in exposed terrain from strong southerly winds.

The storm snow overlies various layers that formed during the cold spell in late December. These layers include a melt-freeze crust on sun-exposed aspects, weak and feathery surface hoar in areas sheltered from the wind, weak and sugary faceted grains, and hardened surfaces from strong wind. There is uncertainty in how long it will take for the storm snow to bond to these layers.

A weak layer of faceted grains may be found above a widespread melt-freeze crust that formed in early December. This layer is likely found anywhere from 100 to 250 cm deep. This layer was the culprit of large, destructive avalanches in December. It has been most reactive between 1700 and 2100 m.

The lower snowpack is well-settled and strong.

Terrain and Travel

  • Choose conservative terrain and watch for clues of instability.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Stick to simple terrain and be aware of what is above you at all times.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.