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Avalanche Forecast

Archived

Mar 4th, 2022–Mar 5th, 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 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.

Regions

South Coast Inland.

A weak crust/facet layer is creating a persistent slab problem in the neighbouring Sea to Sky region which has resulted in numerous recent avalanches. Conditions are expected to be similar for the north of the Inland region. Check out the new forecaster blog for more details.

Confidence

Low - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather. Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack. Uncertainty is due to the limited number of field observations.

Weather Forecast

A ridge of high pressure brings dry and sunny conditions for the weekend. 

Friday Night: Mainly clear, light to moderate N wind, freezing levels near valley bottom.

Saturday: Sunny, light to moderate N wind, freezing levels reaching around 1500 m.

Sunday: Mainly sunny, moderate N wind, freezing levels potentially reaching as high as 2000 m in the late afternoon.

Monday: Mainly cloudy, moderate to strong NW wind, freezing levels 1200-1500 m.

Avalanche Summary

On Thursday, some natural wet slabs up to size 1.5 were reported in the north of the region as well as several natural wind slabs. Natural loose avalanches were also observed on steep sun-exposed slopes. In the Coquihalla, a few glide slab avalanches were observed. 

In the neighbouring Sea to Sky region, numerous natural and human-triggered persistent avalanches have been observed over the past few days. The snowpack structure is expected to be similar in the north of the region and persistent slab problem should be expected until proven otherwise.

On Wednesday, numerous storm slab and loose wet avalanches up to size 2 were reported. Treeline and below treeline terrain saw wet loose avalanches up to size 2 as well. In the neighboring Sea to Sky region, a few skier controlled and remotely triggered (from as far away as 40 m) avalanches were also reported. These persistent slabs failed on the mid-February facet/ crust interface buried approximately 50 cm down. They caught people by surprise, but no involvements were associated.

Snowpack Summary

Anywhere from 40 cm to 60 cm of recent storm snow has accumulated in the North (Pemberton area) and up to 80 cm in the South (Coquihalla) over a variety of surfaces that were buried mid-February. These old interfaces include surface hoar and/or facets in shady, wind-sheltered areas, sun crust on solar aspects. Generally, the storm snow seems to be settling quickly. The snow was moist/wet and rain-soaked at lower elevations, especially in the southern half of the province, which has most likely resulted in the formation of a new surface crust.

In the neighboring Sea to Sky region on northerly slopes (NW, N, NE, E) at treeline/ low alpine elevations (1600-2000 m) the mid-February facet/ crust persistent weak layer has been touchy to skier triggers, showing signs of whumphing and remotely-triggered avalanches. Reports indicate that areas that have a 3-5 cm thick layer of facets sitting on a hard melt-freeze crust are most concerning. There is no direct evidence of this persistent slab problem in the South Coast Inland region but it may be developing and should be on your radar because the snowpack structure is similar, especially in the north of the region.

Another crust/facet layer from late-January is buried down 40-120 cm and has shown no results in recent snowpack tests and is dormant at this time.

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Minimize exposure to sun-exposed slopes when the 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.