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Avalanche Forecast

Archived

Mar 22nd, 2022–Mar 23rd, 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 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

Kootenay Boundary.

Avalanche danger will increase during periods of strong solar radiation or rain at lower elevations. 

Head out with a conservative mindset and dial back your terrain choices until the weather cools.

Confidence

Moderate - Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

TUESDAY NIGHT: Cloudy. Moderate to strong southwesterly winds. Freezing level around 2500 m.

WEDNESDAY: Cloudy with light precipitation. Moderate to strong southwesterly winds. Freezing level around 2500 m.

THURSDAY: Clear in the morning with increasing cloud cover. Light variable winds. Freezing level around 1700 m.

FRIDAY: Partially cloudy. Light southwest winds. Freezing level around 1700 m.

Avalanche Summary

A few natural and human-triggered wind slabs occurred in the alpine and treeline on Monday (size 1-2). 

There have been some notable human-triggered avalanches in Kootenay Pass and the Nelson area in the past week. These large slab avalanches (size 2), failed on either a buried sun crust on solar aspects or surface hoar on shaded aspects. This MIN report from an incident on Saturday near Whitewater is an example of this problem. 

On Friday, an operator south of Nelson reported a large slab avalanche (size 3), triggered by a helicopter landing initiating a cornice failure. This avalanche stepped down to a deeper weak layer in the upper snowpack, suggesting that these deeper layers are still possible to trigger with large loads.

Snowpack Summary

50 to 70 cm of settling storm snow exists at higher elevations. New snow depths taper significantly with elevation, with moist and crusty surfaces below 1800 m and on south aspects into the alpine. 

Last week's storm snow is bonding poorly to underlying layers in some areas. In the Selkirks, especially north of Nelson, it appears that this snow is bonding poorly to the underlying sun crusts on solar aspects and surface hoar on shaded aspects. In the Monashees, reports suggest that this snow has formed a stronger bond to underlying crusts. Several other crust layers are found 50 to 100 cm deep, and the snow is mostly well bonded to these crusts.

Terrain and Travel

  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Avoid steep slopes when air temperatures are warm, it is raining, or solar radiation is strong.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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.

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.

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.