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Avalanche Forecast

Archived

Dec 31st, 2020–Jan 1st, 2021

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

Regions

South Rockies.

New wind slabs may be forming up high. Good riding conditions remain in terrain that has been sheltered from the wind.

Confidence

High -

Weather Forecast

THURSDAY NIGHT: Cloudy with light snowfall, accumulation 1 to 3 cm, 30 km/h southwest wind, alpine temperature -6 C.

FRIDAY: Cloudy with snowfall, accumulation 5 cm, 40 km/h southwest wind, alpine temperature -5 C, freezing level rising to 1500 m.

SATURDAY: Cloudy with snowfall, accumulation 10 to 20 cm, 40 km/h southwest wind, alpine temperature -5 C, freezing level 1500 m.

SUNDAY: Cloudy with snowfall, accumulation 20 to 40 cm, 40 km/h southwest wind, alpine temperature -4 C, freezing level 1500 m.

Avalanche Summary

No recent avalanches have been reported in the region.

Snowpack Summary

A bit more snow and southwest wind are forecast for Friday. New wind slabs may form in exposed terrain, particularly in the alpine. In sheltered terrain, soft snow is likely found. You may find this recent snow overlying a hard melt-freeze crust below 1900 m.

Weak layers of feather surface hoar and/or sugary faceted grains may be found above a hard melt-freeze crust around 40 to 90 cm deep. Avalanches were reported on these layers on December 23 and 25.

The base of the snowpack consists of faceted grains and a hard melt-freeze crust from early-November. The most recent activity on this layer was on December 23.

Terrain and Travel

  • Carefully evaluate steep lines for wind slabs.
  • Avoid slopes that sound hollow or drum-like.
  • Be aware of the potential for large avalanches due to the presence of buried weak layers.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.