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Avalanche Forecast

Archived

Jan 15th, 2021–Jan 16th, 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 and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Northwest Coastal.

The stormy weather pattern continues for the Northwest Coast, keeping danger elevated. Avoid avalanche terrain.

The likelihood of natural avalanches will increase throughout the day with heavy snow and strong wind.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

FRIDAY NIGHT - Mainly cloudy with a few flurries / southwest wind, 40-60 km/h / alpine low temperature near -5 / freezing level 1000 m, and near valley bottom in the far north (Ningunsaw)

SATURDAY - Snow, 10-20 cm, with another 10-20 cm overnight / southwest wind, 50-70 km/h / alpine high temperature near -2 / freezing level 1000 m in the south, near valley bottom in the north 

SUNDAY - Flurries, 5-10 cm / southwest wind, 30-60 km/h / alpine high temperature near -2 / freezing level 1000 m in the south, near valley bottom in the north

MONDAY - Mainly cloudy / southwest wind, 30-60 km/h / alpine high temperature near -2 / freezing level 1500 m in the south, 1000 m in the north

Avalanche Summary

Continued stormy weather will mean that storm slabs are anticipated to be widespread and natural avalanches are expected. Wet loose avalanches may still be possible at lower elevations in the south.

There were a few natural and explosives triggered size 1-3 avalanches reported in the north of the region on Thursday.

There were a few natural avalanches up to size 3 reported in the north of the region on Wednesday. There was also one remotely triggered size 3 persistent slab avalanche reported in the north of the region.

There was a natural avalanche cycle reported on Tuesday, as well as numerous explosives triggered avalanches up to size 2.5 and a few human triggered size 1 avalanches.

On Monday, there were reports of widespread natural and explosives triggered avalanches up to size 3. The largest avalanches were reported in the north of the region where there has been more recent snow. The avalanches being reported closer to Terrace were generally in the size 1-2 range.

Snowpack Summary

10-20 cm of snow is expected during the day on Saturday, bringing recent storm snow totals to around 80-140 cm. 

The snow is likely wet up to treeline in the south of the region. Further north, the snow may be wet or moist below treeline towards Bear Pass, and to a lesser extent around Ningunsaw. 

In the Shames area, a weak layer of surface hoar has been reported in sheltered areas down around 120-180 cm. 

A bit further north in the Nass/Sterling/Beaupre areas, there is potentially still concern about an older weak layer overlying a crust that is now roughly 180-200 cm deep. 

In the far north of the region, there is concern about weak snow at the bottom of the snowpack.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Avoid avalanche terrain during periods of heavy rain.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.

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.