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Avalanche Forecast

Archived

Mar 18th, 2022–Mar 19th, 2022

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

Regions

Kootenay Boundary.

Uncertainty surrounding buried weak layers in the eastern part of the region is best managed with conservative terrain choices and good travel habits.

Reactive wind slabs may exist at upper elevations. Be cautious as you transition into wind-affected terrain.

Confidence

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

Weather Forecast

Active weather continues, with a series of frontal systems moving inland bringing light to moderate amounts of new snow.

FRIDAY NIGHT: Cloudy with snowfall, up to 5 cm of accumulation. Light to moderate southwesterly winds. Freezing level 1000 m. 

SATURDAY: Snowing, 5-10 cm of accumulation. Moderate to strong southwesterly winds. Freezing level rising to 1500 m, dropping to 500 m overnight.

SUNDAY: Partially cloudy, light flurries. Moderate westerly winds easing in the afternoon. Freezing level rising to 1500 m, dropping to 500 m overnight.

MONDAY: Snowing, 5-10 cm of accumulation. Light to moderate southwesterly winds. Freezing level rising to 1500 m.

Avalanche Summary

Wind slabs are expected to form throughout the day and be reactive to human-triggering in the alpine and exposed areas at treeline.

There have been some notable human-triggered avalanches north of Nelson the past few days in the South Columbia region (read more in this blog). These have been larger storm slabs above weak layers, and we are uncertain whether these are signs of a developing persistent slab avalanche problem that could begin impacting northern and eastern parts of the Kootenay Boundary region as well.

A natural cycle occurred during Tuesday's storm. The cycle involved many large storm slab avalanches in the top 20 to 40 cm of snow (size 2). On Wednesday, activity was limited to a few natural slab and loose avalanches triggered by warming on south-facing slopes (size 1 to 2).

Snowpack Summary

10 to 15 cm of new snow overlies last week's 30 to 50 cm of denser, more settled snow. There is uncertainty about how well last week's snow is bonding to underlying layers. In the Selkirks, especially north of Nelson, it appears this snow could be bonding poorly to underlying crust and surface hoar layers. In the Monashees, it appears this snow has formed a stronger bond to underlying crusts. At this point, it appears persistent slab problems could be developing in the deeper snowpack areas in the Selkirks. There are several other crust layers found 30 to 70 cm deep, and it appears the snow is mostly well bonded to these crusts.

Terrain and Travel

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Approach steep, open and/or sparsely treed slopes cautiously.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Investigate the bond of the recent snow before committing to your line.

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.