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Avalanche Forecast

Archived

Jan 10th, 2020–Jan 11th, 2020

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

Regions

North Columbia.

Watch for areas where the new snow feels stiff or slabby and remain cautious of open slopes and convex rolls.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

FRIDAY NIGHT: Cloudy with isolated flurries and 5-10 cm of snow, light wind from the southwest, alpine temperatures drop to -14 C.

SATURDAY: Cloudy with scattered flurries and 5-10 cm of snow, light wind from the west, alpine high temperatures around -10 C.

SUNDAY: Scattered flurries with 5-10 cm of snow, light wind, alpine high temperatures around -12 C.

MONDAY: Mostly sunny, light wind from the southwest, alpine high temperatures around -20 C.

Avalanche Summary

Avalanche activity is likely on the decline as only moderate accumulations of low density snow are expected over the weekend, although there is uncertainty about whether wind could be forming fresh slabs at higher elevations.

Wednesday's storm resulted in widespread avalanche activity with numerous large and very large avalanches (size 2-3). Both storm slab and persistent slab avalanches were reported across aspects and elevations during this period. Persistent slab avalanches were breaking a meter deep, and one of them was remote-triggered. By Thursday the layer was less reactive with only explosive triggered avalanches reported. Preliminary reports from Friday suggest the most recent low density snow was sluffing and producing thin soft slabs.

Snowpack Summary

Low density snow continues to accumulate. Most areas likely have 20-30 cm of soft snow, but stiffer and reactive slabs could be forming in terrain affected by the wind. Recent storms have buried two layers of surface hoar from late December now down 80-140 cm deep. These layers produced large to very large avalanches across all aspects and elevations over the past week.

Terrain and Travel

  • Sheltered slopes at lower elevations will offer the best riding.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.