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

Regions

Cariboos.

A dangerous dilemma exists in sheltered, shaded areas where dry powder may be preserved, but a lethal layer of surface hoar could remain ripe for human triggering.

These beautiful warm sunny days are best enjoyed in low angled alpine terrain with no exposure to overhead hazard.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

A ridge of high pressure continues to bring mainly clear skies and dry conditions into Saturday. 

Friday Overnight: Mainly clear. Freezing level dropping to valley bottom. Moderate to strong northwest winds at ridgetop. 

Saturday: Mainly clear, some valley cloud may develop. Freezing level rising to 1300 m with an alpine temperature inversion. Light to moderate northwest winds at ridgetop.

Sunday: Cloud cover increasing. Freezing level rising to 1000m. Light to moderate westerly winds at ridgetop.

Monday: Snowing. Freezing level rising to 1000 m in the afternoon. Light to moderate westerly winds at ridgetop.

Avalanche Summary

Operators observed several natural and human-triggered wind slabs on Thursday in lee areas in the alpine as strong northwesterly winds redistributed available snow. One notable persistent slab result in the south of the region occurred in a wind-loaded feature in the alpine on the January 30th surface hoar layer.

As a result of the rain event on Wednesday, operators observed a large natural avalanche that initiated as a storm slab in the alpine and gouged to ground lower down in the track in wet, uncohesive snow.

Throughout the week, sporadic reports of human-triggered avalanches on the January 30th weak layer have indicated that this layer remains problematic and has the potential to surprise riders with large, consequential avalanches.

Snowpack Summary

Overnight, clear skies and cooling temperatures will refreeze the surface of the snowpack. A thin breakable crust exists on almost all aspects and elevations, while a thicker more prominent crust can be expected at lower elevations and on south-facing aspects. Warm daytime temperatures and strong solar radiation will likely cause these crusts to break down throughout the day.

Strong westerly winds throughout the week have created extensive wind-effect in open areas at all elevations. Expect to find old and new wind slabs on a variety of aspects, with the most recent and reactive slabs formed in terrain features lee to the northwest. 

Several weak layers exist in the upper snowpack including buried crusts, facets, and a prominent weak layer of surface hoar. This surface hoar is the dominating feature. It was buried in late January and exists 60 to 100 cm deep in the snowpack. Reports suggest that the surface hoar is most prominent in sheltered openings at and below treeline. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns. 

The lower snowpack is generally strong and well-bonded.

Terrain and Travel

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid steep slopes when air temperatures are warm, or solar radiation is strong.

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.

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.