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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

Vancouver Island.

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 afternoon. 

Confidence

Low - Uncertainty is due to the limited number of field observations. 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 around 2500 m. A storm system is expected to arrive Thursday night which will replace the warm air and linger into Friday morning. 

Wednesday Night: Mainly cloudy, moderate to strong SW wind, freezing level climbing to around 1800 m. 

Thursday: Mainly cloudy in the morning, sunny breaks in the afternoon, strong to extreme SW wind, freezing level high around 2500 m.

Thursday night: Precipitation 5-10 mm, strong to extreme SW wind, freezing level 2000 m dropping to around 1200 m.

Friday: Snowfall 5-10 cm in the morning, sunny breaks in the afternoon, moderate NW wind, freezing level high around 1300 m.

Saturday: A mix of sun and cloud in the morning, light snowfall in the afternoon, moderate to strong NW wind, freezing level high around 800 m.

Avalanche Summary

On Tuesday, the Avalanche Canada field team observed a size 1.5 storm slab on a north aspect which was expected to have occurred near the end of the storm on Monday. This MIN report describes numerous size 1-2 storm slabs which had occurred during the storm, primarily on northwest through east aspects resulting from wind loading.  

Observations are very limited this time of year. If you are getting out in the backcountry, please consider sharing your observations to the Mountain Information Network. 

Snowpack Summary

The recent storm is estimated to have produced 60-100 cm of new snow. This storm snow has buried a widespread, supportive melt-freeze crust. Recent observations suggest the new snow is relatively well bonded to this underlying crust but it still has the potential to be a sliding surface for storm slab avalanches during the upcoming warming event. Strong to extreme southwest wind during the storm had redistributed this storm snow in exposed, high elevation terrain forming touchy wind slabs and building large cornices. 

Reports from Tuesday suggest the recent storm snow remains mostly unconsolidated in sheltered terrain. With sun on Wednesday and major warming on Thursday, the storm snow is expected to settle rapidly and form a more cohesive slab which is expected to increase the avalanche danger in the short term. 

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.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.