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Avalanche Forecast

Archived

Feb 28th, 2021–Mar 1st, 2021

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 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

South Columbia.

Wind slabs are likely to be encountered and may be reactive to human triggering. Watch for signs of instability such as whumpfing, cracking, and recent avalanches.

There is still the potential to trigger persistent weak layers. Choose conservative terrain.

Confidence

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

Weather Forecast

SUNDAY NIGHT - Mainly cloudy with isolated flurries / moderate to strong southwest wind / alpine low temperature near -5 / freezing level 1300 m

MONDAY - Mainly cloudy with isolated flurries / moderate to strong southwest wind / alpine high temperature near -6 / freezing level 1500 m

TUESDAY - Mainly cloudy with isolated flurries / moderate southwest wind / alpine high temperature near -5 / freezing level 1200 m

WEDNESDAY - A mix of sun and cloud / light to moderate south wind / alpine high temperature near -6 / freezing level 1500 m

Avalanche Summary

On Saturday, there were a few size 1-2 natural and human-triggered wind and storm slab avalanches reported. There were also several reports of explosives triggered size 2-3 storm slab avalanches reported near New Denver.

Since Tuesday, 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.

During the storm last weekend and into last Monday, there was a widespread natural and explosives-triggered avalanche cycle, with avalanches ranging from size 2-4. 

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

The region has received 60-100 cm of fresh snow in the past week. Deep wind deposits may be found in lee terrain features in the alpine and open treeline areas, and will likely remain reactive to human triggers. All of this new snow sits over weak, faceted snow from the early to mid-February cold snap. 

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 recently.

Terrain and Travel

  • Be carefull around freshly wind loaded features.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.

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.