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Avalanche Forecast

Archived

Feb 6th, 2022–Feb 7th, 2022

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

Regions

Northwest Inland.

Riders could trigger touchy wind slabs at higher elevations.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

SUNDAY NIGHT: Cloudy with snowfall, accumulation 5 to 10 cm, 40 km/h southwest wind, alpine temperature -5 C, freezing level 1100 m.

MONDAY: Cloudy with snowfall, accumulation 5 cm, 50 km/h southwest wind, alpine temperature -5 C, freezing level 1000 m.

TUESDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 60 km/h southwest wind, alpine temperature -3 C, freezing level 1300 m.

WEDNESDAY: Cloudy with snow and rain, accumulation 5 to 15 cm above 1800 m and rain below, 60 km/h southwest wind, alpine temperature 0 C, freezing level 1800 m.

Avalanche Summary

Many large (size 2) wind slab avalanches were observed on Friday and Saturday, being triggered naturally and by riders (for example, here).

Looking forward, similar avalanches are expected to be triggerable by riders as the slabs continue to form.

Snowpack Summary

Strong southwest wind and continual small amounts of snow have formed wind slabs in lee terrain features at higher elevations. Storm slabs may also be building in sheltered terrain. These slabs may take a bit of time to bond to the snowpack, particularly where they sit on weak faceted snow or surface hoar crystals. The snow tapers with elevations. Below around 1300 m, only a small amount of snow overlies a hard melt-freeze crust. Below around 1000 m, any precipitation is forecast to fall as rain, which will soak a previously wetted snowpack.

Two weak layers may exist around 50 to 100 cm deep in the snowpack. The first is a surface hoar layer from mid-January and the second is a layer of faceted snow from early January. These layers haven't produced recent avalanches, but the potential remains until these layers bond to the snowpack.

Terrain and Travel

  • Stay off recently wind loaded slopes until they have had a chance to stabilize.
  • Wind slabs are most reactive during their formation.
  • Start with conservative lines and watch for clues of instability.
  • Make observations and assess conditions continually as you travel.

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.