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Avalanche Forecast

Archived

Mar 26th, 2021–Mar 27th, 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 and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
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.

Regions

Northwest Coastal.

A juicy storm is expected to deliver heavy snow with strong winds to the Northwest Coast. Travel in avalanche terrain is not recommended.

Confidence

Moderate - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

FRIDAY NIGHT - Snow, 15-20 cm / strong west wind / alpine low temperature near -2 / freezing level 1000 m 

SATURDAY - Snow, 25-35 cm, with another 10-20 overnight / extreme southwest wind / alpine high temperature near -2 / freezing level 1000 m 

SUNDAY - A mix of sun and cloud with scattered flurries / moderate northwest wind / alpine high temperature near -5 / freezing level 800 m 

MONDAY - Cloudy with sunny periods and scattered flurries / strong northwest wind / alpine high temperature near -5 / freezing level 800 m

Avalanche Summary

Natural avalanche activity is expected to be widespread throughout the day on Saturday with heavy snow and strong winds in the forecast.

On Thursday, Explosive control work conducted east of Kitimat resulted in cornices failures up to size 2.5, and wind slabs limited to size 1. Dry loose avalanches were also observed up to size 1.5. Around Ningunsaw, there were explosive-triggered avalanches up to size 3, including one that is suspected to have failed on the mid-February persistent weak layer.

Tuesday's storm resulted in a widespread natural avalanche cycle, with size 2-3 storm slab avalanches at upper elevations, and size 1-1.5 wet loose avalanches below treeline.

Several size 2-3 natural glide slab avalanches have been reported over the last week. Avoid slopes with glide cracks on them at all times. They are inherently unstable and can release at any time.

Snowpack Summary

15-20 cm is expected on Friday night, with another 25-35 during the day on Saturday. Storm slabs are expected to be widespread and reactive at upper elevations. Below treeline may see heavy rainfall associated with this storm.

A crust is now buried 75-100 cm below the surface on solar aspects and below 1400 m. At higher elevations where this crust tapers out, the new snow has added significant load to a couple of deeply buried weak layers that we haven't quite ruled out as problems.

The first and most concerning persistent weak layer was buried in mid-March and is around 100-140 cm deep. It consists of surface hoar on sheltered northerly aspects around treeline. 

Down between 150 to 300 cm is another layer of surface hoar and facets, buried in mid-February. This layer may still be a concern in shallower snowpack areas. 

There is a chance that further loading during the incoming storm could result in some large persistent slab avalanches.

The mid and lower snowpack is well settled and strong in most areas.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Storm slab size and sensitivity to triggering will likely increase through the day.

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.

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.