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Avalanche Forecast

Archived

Feb 9th, 2022–Feb 10th, 2022

Alpine
Natural avalanches possible, human triggered probable.
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 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.

Regions

Kootenay Boundary.

Keep an eye on daytime warming and solar input. There is some uncertainty in how the snowpack will react to the rising freezing levels. . Avoid overhead hazard.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

Wednesday night: no new snow expected. Light to moderate northwest winds. Inverted temperatures with above freezing levels treeline and above. Sub zero temperatures and valley fog down low.

Thursday: Mainly sunny with light to moderate west wind. Freezing levels reaching over 2500 m with an inversion.

Friday: sunny with freezing levels around 1500m. Light northwest winds.

Saturday: sunny with freezing levels rising to 1800m. Light northwest winds.

Avalanche Summary

On Tuesday explosives triggered persistent slab avalanches up to size 3 on northeast aspects at 2200m. These avalanches ran on the late January surface hoar and showed substantial propagation.

On Monday numerous persistent slab avalanches to size 2.5 were observed in the treeline and below. triggers included cornice falls, ski cuts and naturals. Avalanches were observed on all aspects.

On Sunday, several natural loose wet avalanches up to size 1.5 were reported. A skier triggered a size 1.5 slab on a NW aspect at 1900 m which failed down 30 cm. Just north of the region, a natural size 3.5 persistent slab was reported on a SE aspect at 2200 m which stepped down to a layer around 100 cm deep, propagated close to 1 km wide, and ran full path.

Snowpack Summary

Moist snow will likely be observed on all aspects treeline and below as well as on solar aspects in the alpine. Recent strong wind from the south have formed wind slabs in exposed terrain at higher elevations. 

The January 30 interface is now typically down 20-50 cm and consists of a melt-freeze crust at lower elevations and on solar aspects extending into the alpine and surface hoar in sheltered areas at and below treeline.  

The mid-January interface is now down around 40-70 cm and consists of a crust, facets, and/or surface hoar.   

The early-December crust/facet persistent weak layer is buried down 100-200 cm. It had been responsible for significant avalanche activity in this region during the first half of January but is now considered dormant. See this forecaster blog on how to manage this layer as it may come into play again later this season.

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of buried weak layers.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • Be careful as you transition into wind affected terrain.

Problems

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.