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

Regions

Sea To Sky.

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: Mainly cloudy, light to moderate SW wind, freezing level climbing to around 1800 m. 

Thursday: Mainly cloudy in the morning, a mix of sun and cloud in the afternoon, moderate to strong SW wind, freezing level high near 2700 m.

Thursday night: Precipitation 20-50 mm, strong 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 SW wind, freezing level high around 1500 m.

Saturday: Mainly cloudy with sunny breaks, light to moderate W wind, freezing level high around 800 m.

Avalanche Summary

On Tuesday, skiers triggered a few avalanches including a size 1.5 storm slab on a steep west aspect at 2000 m, a size 1 avalanche in a steep north aspect couloir at 2150 m, and a remotely triggered size 2 storm slab from 2 m away. A ski cut triggered a size 1.5 cornice release on a northwest aspect at 1900 m. Explosives triggered numerous size 1-2.5 storm slabs and cornices up to size 2.5. The storm slabs were typically up to around 60 cm thick and many were sliding on the underlying melt-freeze crust. Several of the cornice releases triggered slabs on the slopes below. 

A variety of older avalanches were also reported on Tuesday which had occurred during the storm including evidence of a natural size 2 storm slab cycle. A natural cornice release was observed which triggered a size 3 storm slab and a few other natural cornice releases which triggered size 2 storm slabs.

Snowpack Summary

The recent storm produced 60-80 cm of new snow in the Whistler area. 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 has redistributed the new storm snow in exposed, high elevation terrain forming wind slabs up to 150 cm thick and developing large cornices. Windward slopes have been scoured down to the crust and the alpine snow surface is expected to be highly variable. A new sun crust was reported to be forming on the snow surface on Tuesday. 

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.