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Avalanche Forecast

Archived

Feb 11th, 2022–Feb 12th, 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 possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Kootenay Boundary.

When in doubt ride simple terrain. The likelihood of triggering avalanches could change rapidly with warming and solar input. There is some uncertainty in where and when slab properties could exist above the late January layer. Use caution at treeline and avoid overhead hazard.

Confidence

Low - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Friday night: no new snow expected. Low of -6 at 1500m and light to moderate northwest winds.

Saturday: sunny with a temperature inversion and a above freezing layer between 2000m and 2500m. Light to moderate northwest winds.

Sunday: sunny with freezing levels rising to 1800m and the possibility of a temperature inversion. Light southwest winds.

Monday: light precipitation bringing up to 5cm of snow. Light southwest winds and freezing levels rising to 1500m.

Avalanche Summary

On Thursday two size 1 persistent slab avalanches were triggered by skiers on east aspects at treeline. In the southern part of the neighboring South Columbia region a vehicle triggered a size 3 avalanche at treeline running on the early December crust. This avalanche was on a northeast aspect and ran full path. 

On Wednesday a skier triggered a size 2 persistent slab avalanche just below a ridge top at 2100m on a northeast aspect. This avalanche ran on the late January surface hoar.

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.

Snowpack Summary

A new crust has formed on all aspects and elevations except high north terrain. This crust could soften throughout the day with rising temps and sun exposure. Recent strong wind from the southwest have formed wind slabs in exposed terrain at higher elevations. 

The January 30 interface is now typically down 20-40cm 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.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
  • 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.