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Avalanche Forecast

Archived

Mar 2nd, 2021–Mar 3rd, 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 avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Columbia.

Use extra caution around slopes exposed to the sun and high elevation terrain that has been wind affected.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

TUESDAY NIGHT: Mostly cloudy, moderate southwest wind, treeline temperatures drop to -8 C.

WEDNESDAY: Mix of sun and cloud, light southwest wind, freezing level climbs to 1500 m with treeline temperatures around -2 C.

THURSDAY: Sunny, light south wind, freezing level climbs to 1800 m with treeline temperatures around 0 C.

FRIDAY: Mostly sunny, light south wind, freezing level climbs to 1700 m with treeline temperatures around -1 C.

Avalanche Summary

Since the storm and associated avalanche cycle eased off early last week, there have been daily reports of size 1-2 natural and human-triggered avalanches in many areas. There have also been reports of larger (size 2-3) explosives triggered avalanches on most days. The size and frequency of these avalanches have generally decreased slightly each day.

There have been a few reports of sporadic persistent slab avalanches failing on the late January persistent weak layer in the past month, including one in the past week. 

Snowpack Summary

There is around 60-100 cm of snow sitting on a persistent weak layer of facets that was buried in mid-February. Deep wind deposits and wind slabs exist in the alpine and open treeline areas, while a thin surface crust has been reported at most elevations. Surfaces are likely starting to melt and freeze on southern slopes and at lower elevations.

There is now 80-120 cm of snow above the late January persistent weak layer which is composed of surface hoar in sheltered areas in the trees and/ or a crust on steep solar aspects. Very isolated activity on this layer has been observed in the past few weeks.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.