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Avalanche Forecast

Archived

Mar 3rd, 2021–Mar 4th, 2021

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
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.

Regions

Northwest Coastal.

Natural avalanche activity will likely occur on Thursday, especially when the freezing levels are forecast to rise to the mountain tops! The snowpack will need more time to adjust and settle out. Its a good time to be patient and conservative. 

Confidence

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

Weather Forecast

Wednesday Night: Snow amounts 10-20 cm and ridgetop wind moderate from the South. Alpine temperatures near -3 and freezing levels 600 m.

Thursday: Mostly cloudy with some sunny periods and snow 5-15 cm. Ridgetop wind light with strong gusts from the southeast. Alpine temperatures 0 degrees and freezing levels 1200 m. 

Friday: Cloudy with sunny periods and isolated flurries. Ridgetop wind moderate from the South. Alpine temperatures near -4 and freezing levels 700 m. 

Saturday: Mix of sun and cloud with ridgetop wid light from the South. Alpine temperatures near -5 and freezing levels 500 m.

Avalanche Summary

On Wednesday, a notable persistent slab size 3 was reported. It was possibly a day old, however; the suspect failure plane was the mid-February weak layer. Numerous natural storm slabs were also reported.

Over the weekend a widespread natural avalanche cycle occurred up to size 3 and explosive control initiated numerous size 2-3 storm slabs and persistent slabs.

The storm looks to taper off Thursday however snowfall amounts due vary across the region. With rising freezing levels and all of this recent snow and wind, the avalanche danger will remain elevated through the day.

It's a good time to stay very conservative, stick to simple terrain, and be aware of overhead hazards like large avalanche paths and cornices. 

Snowpack Summary

60-100 cm of recent storm snow blanketed the region over the past week. This was accompanied by strong to extreme southwest winds building deeper wind slabs on leeward slopes. Massive cornices exist on ridgelines at treeline and in the alpine. Below treeline moist snow sits on a melt-freeze crust. 

Snowfall accumulation now brings 1-2 metres over the plethora of old snow surfaces buried mid-February and deeper down buried late January. These old persistent weak layers comprise of hard wind-packed snow, feathery surface hoar crystals especially in areas sheltered from the wind, and sugary faceted snow that developed during the cold snap. These weak layers have been the result of several larger avalanches in the past week. 

The mid-pack has been reported as being well-settled. There are presently no deeper concerns 

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Avoid exposure to overhead avalanche terrain as temperatures increase.
  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.