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Avalanche Forecast

Archived

Feb 27th, 2021–Feb 28th, 2021

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

Regions

North Columbia.

Watch for changing conditions as strong winds may mean that storm slabs become increasingly reactive throughout the day. Avoid overhead hazard during times of rapid loading due to strong winds.

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

Confidence

Moderate - Forecast snowfall amounts are uncertain. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

SATURDAY NIGHT - Cloudy with flurries, 5-10 cm / moderate to strong southwest wind / alpine low temperature near -12 

SUNDAY - Mainly cloudy with scattered flurries, 5 cm / strong west wind / alpine high temperature near -5 / freezing level 1500 m

MONDAY - Mainly cloudy / strong southwest wind / alpine high temperature near -6 / freezing level 1500 m

TUESDAY - Mainly cloudy with flurries / moderate southwest wind / alpine high temperature near -7 / freezing level 1300 m

Avalanche Summary

On Friday, there were several reports of size 1-1.5 human triggered avalanches, as well as one size 2.5 natural avalanche at 2250 m on a southwest to west aspect. 

There was also a report of a human-triggered size 2 avalanche that resulted in a full burial in a cutblock near Blue River on Friday. Check out the MIN report here.

On Thursday, there were numerous reports of human-triggered size 1-1.5 storm slab, wind slab, and dry loose avalanches. There were also a few reports of natural avalanches up to size 3 in the neighbouring Glacier National Park region.

On Wednesday there were two explosives-triggered size 3 persistent slab avalanches reported on east to southeast aspects around treeline. These were notable as they failed on the late January persistent weak layer.

There was a widespread natural and explosives-triggered avalanche cycle last weekend and into Monday, with avalanches reported up to size 4. The largest of these avalanches were reported in the Selkirks.

Snowpack Summary

5-10 cm of snow on Saturday night adds a little refresh to the 60-100 cm that has fallen 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 recent cold snap. 

There is now 70-120 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. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be aware of highly variable recent wind loading patterns.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Use conservative route selection and resist venturing out into complex terrain.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.