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Avalanche Forecast

Archived

Apr 5th, 2022–Apr 6th, 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 possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

South Coast.

This forecast has been produced with very few recent observations. It will be important to continually assess your local conditions throughout the day. 

The recent storm snow is expected to remain reactive to human triggering, especially in wind-loaded terrain. 

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.

Weather Forecast

A ridge of high pressure brings sunny conditions for Wednesday morning but cloud from a storm system impacting the north coast is expected to spill into the region by the afternoon. 

Tuesday Night: Mainly clear, light variable wind, freezing level low around 800 m. 

Wednesday: Mainly sunny with increasing cloud cover in the afternoon, light to moderate SW wind, freezing level high around 1700 m.

Thursday: Mainly cloudy with sunny breaks in the afternoon, moderate SW wind, freezing level high around 2500 m.

Thursday night and Friday: Precipitation 25-40 mm, sunny breaks in the afternoon, moderate to strong SW wind, freezing level falling to around 1200 m. 

Avalanche Summary

On Monday, some natural storm slab avalanches were observed which had occurred Sunday overnight and had crowns up to 50 cm thick but only limited propagation. Explosives also triggered a few small storm slabs which were typically around 30 cm thick. This MIN report from the Cypress area describes ski cutting with no results suggesting the recent storm snow is stabilizing quickly. 

On Sunday morning, ski cutting was triggering touchy size 1 storm slabs above 1100 m elevation and stubborn size 1 wet loose avalanches below 1100 m elevation. This MIN post and this MIN post from Sunday both describe touchy conditions including several small natural slab avalanches.

Snowpack Summary

The recent storm appears to have produced around 40-50 cm of new snow for the North Shore mountains and 70-90 cm closer to Squamish. This storm snow has buried a widespread, supportive melt-freeze crust. Strong southwest wind has likely redistributed this new snow in exposed, high-elevation terrain forming touchy wind slabs. This MIN post describes a new surface crust in the North Shore mountains which may be reducing the avalanche hazard in that area but observations have been very limited and the mountains around Squamish may have a snowpack more similar to the Sea-to-Sky region. 

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

Terrain and Travel

  • Make observations and assess conditions continually as you travel.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • 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.

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.

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.