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Avalanche Forecast

Archived

Apr 6th, 2022–Apr 7th, 2022

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
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 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.

Major warming with periods of strong spring sun are expected to create dangerous avalanche conditions on Thursday and a natural avalanche cycle is possible in the afternoon. 

Check out this new blog post for examples of avalanche activity we may see Thursday. 

Confidence

Low - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack. Uncertainty is due to rapidly fluctuating freezing levels.

Weather Forecast

A major warming event is forecast for Thursday with freezing levels climbing to at least 2500 m. A storm system is expected to arrive Thursday night which will replace the warm air and linger into Friday morning. 

Wednesday Night: Partly cloudy, light to moderate SW wind, freezing level low around 1500 m/high around 2000 m. 

Thursday: Mainly sunny, moderate to strong SW wind, freezing level high near 2500 m in the north, 3000 m in the south.

Thursday night: Precipitation 5-10 mm, strong SW wind, freezing level 2500 m dropping to around 1300 m.

Friday: Snowfall 5-10 cm in the morning, a chance of sunny breaks in the afternoon, moderate to strong SW wind, freezing level high around 1600 m.

Saturday: Mainly cloudy with sunny breaks and a chance of flurries, light to moderate W wind, freezing level high around 1000 m.

Avalanche Summary

An early report from Wednesday includes three explosive-triggered size 1.5-2 wind slabs in the north of the region on northwest and north aspects at 2200 m.  

On Tuesday, a skier remotely triggered two size 1 storm slabs from 2 m away on a northeast aspect at 2000 m in the north of the region. These were 30 cm thick and failed on the underlying melt-freeze crust. In the Coquihalla area, a few natural size 1 storm slabs were reported. 

Several older avalanches were also reported on Tuesday which had occurred during the storm including evidence of a natural cycle up to size 2.5 in the north of the region and a few natural cornice releases which triggered size 2 slabs failing on the underlying crust. 

Snowpack Summary

The recent storm produced around 30-50 cm of new snow in the north of the region and around 40-70 cm in the south of the region. This storm snow has buried a firm crust which extends to mountain top on solar aspects and to around 2200 m on northerly aspects. This crust has been the sliding surface for many of the recent storm slab avalanches. Strong to extreme southwest wind during the storm has redistributed the new storm snow in exposed, high elevation terrain forming wind slabs and developing large cornices. Windward slopes have been scoured down to the crust and the alpine snow surface is expected to be highly variable. 

The middle and lower snowpack are generally strong and well bonded. 

Terrain and Travel

  • Watch for changing conditions today, storm slabs may become increasingly reactive.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • Remember that in the spring strong solar radiation and warm temperatures can weaken the snow in a matter of minutes.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.