Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Mar 21st, 2022–Mar 22nd, 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 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.

Regions

Kootenay Boundary.

Avalanche danger will increase as temperatures rise throughout the day. There is uncertainty around how the snowpack will handle this warm-up. 

Choose increasingly conservative terrain as temperatures rise.

Confidence

Moderate - Uncertainty is due to whether buried persistent weak layers become active, triggering avalanches, with the arrival of the forecast weather. Uncertainty is due to the fact that cornice falls are particularly difficult to forecast.

Weather Forecast

MONDAY NIGHT: Cloudy with light flurries. Light westerly winds. Freezing level around 1300 m.

TUESDAY: Mainly cloudy with light flurries. Light to moderate westerly winds. Freezing level rising to 2500 m and staying elevated for the overnight period. 

WEDNESDAY: A Cloudy morning, clearing into the afternoon. Moderate to strong southwesterly winds. Freezing level around 2500 m.

THURSDAY: Mainly clear. Light northerly winds. Freezing level around 1500 m. 

Avalanche Summary

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. 

Several natural storm slabs occurred overnight on Saturday with heavy snowfall. A few human-triggered storm slabs occurred on Sunday throughout the region in the alpine and treeline (size 1-2). 

On Friday, an operator south of Nelson reported a large slab avalanche, 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

10 to 15 cm of recent snowfall overlies last week's 50 to 70 cm of denser, more settled snow. 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 snow is bonding poorly to underlying layers in some areas. In the Selkirks, especially north of Nelson, it appears this snow is bonding poorly to the underlying sun crusts on solar aspects and surface hoar on shaded aspects. In the Monashees, it appears 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.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.