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Avalanche Forecast

Archived

Jan 21st, 2020–Jan 22nd, 2020

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

Regions

Kootenay Boundary.

Recent southerly winds have promoted wind slab development at upper elevations. 

Confidence

Moderate -

Weather Forecast

TUESDAY NIGHT - Flurries, 5 cm / southwest wind, 20-30 km/h / alpine high temperature near -5

WEDNESDAY - Cloudy with isolated flurries / southwest wind, 20-30 km/h / alpine high temperature near -4

THURSDAY - Flurries, 5-10 cm / southwest wind, 30-40 km/h / alpine high temperature near 0 / freezing level 1500 m

FRIDAY - Flurries, 5-15 cm / south wind, 20-40 km/h / alpine high temperature near 0 / freezing level 1500 m

Avalanche Summary

Reports on Monday indicate a few explosives controlled storm slab avalanches size 1.5 to 2 on north and east aspects between 2000 and 2200 m. These were reported as 15-30 cm deep.

On Sunday there was a report of an explosives triggered size 2.5 loose snow avalanche.

No new persistent slab avalanches were observed in the past few days, but this region has been highlighted for recent persistent slab avalanche activity. A number of natural and explosives triggered persistent slab avalanches up to size 3 were reported just over a week ago.

Snowpack Summary

35 to 65 cm of new snow from last weekend has been redistributed by moderate to strong winds from a variety of directions. This combined with relatively warm temperatures, will have likely formed fresh slabs in many areas.

There are two weak layers of surface hoar found around 70 to 130 cm below the snow surface. These layers are especially concerning in steep, sheltered, and shallow rocky areas.

The base of the snowpack in many parts of the region consists of weak sugary faceted crystals around a melt-freeze crust.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of buried weak layers.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

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.

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.