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Avalanche Forecast

Archived

Mar 17th, 2022–Mar 18th, 2022

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

South Coast Inland.

Reactive new wind slabs are expected to be the primary concern for Friday. However, if the sun makes an appearance during the afternoon, solar-triggered loose avalanches are also possible. 

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Unsettled conditions are expected for Friday before a weak storm system arrives early Saturday morning bringing light snowfall through most of Saturday. 

Thursday night: Mainly cloudy with flurries, light to moderate SW wind, freezing level around 1000 m. 

Friday: Mainly cloudy with a chance of both flurries and sunny breaks, light to moderate SW wind, freezing level reaching around 1400 m. 

Saturday: Snowfall 5-15 cm, moderate S-SW wind, freezing level around 1300 m. 

Sunday: A mix of sun and cloud, light W wind, freezing level around 1200 m. 

Avalanche Summary

On Wednesday, several natural storm slabs up to size 1.5 were observed in the Coquihalla area which occurred in the prior 24 hours. A small natural glide slab was also reported. In the north of the region, numerous natural size 1-1.5 wind slabs were reported on north and east aspects in the alpine. 

On Tuesday, a natural size 2 storm slab was reported in the Coquihalla area as well as a natural size 1.5 wind slab on northeast aspect at 1900 m. In the north of the region, several human-triggered storm/wind slabs were reported up to size 2. These were on a variety of aspects between 1850 and 2400 m elevation. Slab thickness varied from 20-60 cm and a few were reported to be sliding on the underlying crust which was buried around March 12. 

Snowpack Summary

Prior to Thursday's snowfall, 20-40 cm of older storm snow which started accumulating on the weekend overlies a melt-freeze crust on sun-exposed aspects and wind-affected or well-settled old snow on shaded aspects. Recent observations suggest this snow is relatively well bonded to the underlying surface. Recent and ongoing wind has redistributed the storm snow into reactive wind slabs in exposed terrain. 

In the north of the region, a crust/facet interface from February sits 30-60 cm deep and had been most problematic on north to northeast aspects around 1900-2100 m. This layer produced a number of avalanche in early March but is now considered dormant and no longer seems to be creating a problem in the region.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Minimize exposure to steep, sun exposed slopes, especially when the solar radiation is strong.

Problems

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.