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Avalanche Forecast

Archived

Jan 21st, 2022–Jan 22nd, 2022

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

Regions

Northwest Coastal.

Watch for changing conditions as a rise in temperature tests the upper snowpack. The presence of buried surface hoar below the storm snow means that reactivity could persist into today.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Stormy weather continues up north, while the south of the region sees a temperature inversion ushering in warm temperatures at higher elevations. 

Friday Overnight: Cloudy, with up to 5 cm of new snow in the north of the region. Strong to extreme southwest winds. Freezing level around 1000m.

Saturday: In the south of the region, partially cloudy skies with the potential for a temperature inversion with above 0 C temperatures in the alpine. In the north, mainly cloudy, up to 10 cm of new snow, accompanied by moderate to strong southwest winds. 

Sunday: Cloudy, up to 5 cm of new snow accumulation. Moderate to strong westerly winds. Freezing level around 1000m.

Monday: Partially cloudy, light northwest winds. Freezing level rising to 2500m.

Avalanche Summary

On Thursday, numerous natural, human-triggered, and remote-triggered storm slab avalanches up to size 2.5 were observed throughout the region. A buried layer of surface hoar, and below 1300m a thick melt-freeze crust likely contributed to the reactivity and wide propagation of these storm slabs.

Snowpack Summary

On Thursday, 30 to 50 cm of snow fell, with snow switching to rain up to around 1000 m around the Terrace area. Storm slabs rapidly built during the storm along with wind slabs in terrain exposed to the wind from strong southwest wind. In some areas, these slabs overlie a weak layer of buried surface hoar and a hard melt-freeze crust below 1300 m. The presence of these weak layers means reactivity might persist.

A layer of sugary facetted grains may be found about 80 to 130 cm deep, which formed during the cold spell in late December to early January. To date, this layer has only been problematic in the northern half of the region.

The remainder of the snowpack is strong in the south of the region. In the north of the region, the base of the snowpack consists of faceted grains around a melt-freeze crust, which is currently dormant.

Terrain and Travel

  • Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
  • Watch for unstable snow on specific terrain features, especially when the snow is moist or wet.

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.