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Avalanche Forecast

Archived

Apr 22nd, 2021–Apr 23rd, 2021

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

Regions

South Coast.

Change is in the air, but even short periods of sunshine combined with high freezing levels can pack a punch to an already weak snowpack. Loose wet avalanches and wet slab avalanches remain possible on Friday. 

Steer clear of cornices from above and below.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Overnight Thursday: Clear with some cloud cover and a light wind. Alpine temperatures near +3 and freezing levels 1600 m. 

Friday: Mostly cloudy with some sunny periods. Ridgetop wind light to moderate from the South. Alpine temperatures near +3 and freezing levels 1600 m.

Saturday: Precipitation 10-20 mm falling as snow in the high alpine and rain below. Ridgetop wind moderate from the South. Alpine temperatures near 0 and freezing levels 1400 m.

Sunday: Precipitation 5-10 mm. Ridgetop wind light from the South. Alpine temperatures near -2 and freezing levels 1300 m. 

Avalanche Summary

No recent avalanche observations have been submitted from this region.

In the neighboring Sea to Sky region and the South Coast Inland, multiple wet slab avalanches and wet loose avalanche activity have been active throughout the week as large as size 4 but primarily in the size 2-3 range. Many of these involved the full depth of the snowpack, running to the valley bottom. We suspect similar activity to have occurred in the South Coast region as well.

Cornices remain weak and fragile. They require a large berth from above and below as they are very unpredictable. 

Snowpack Summary

High overnight freezing levels continue, the snowpack is reportedly isothermal on southerly aspects to the mountain top and all aspects to treeline elevations. A cooling trend will slowly begin tonight forming a surface crust at upper elevations. In places where the surface forms a crust overnight, it should quickly soften during the day with sunshine and warm temperatures. The highest elevation north aspects (above 2200 m) may still hold some dry snow.

Cornices are large and looming along ridgelines. They are weak and very unpredictable.

Terrain and Travel

  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Keep in mind that wet avalanches can be destructive due to their high density.
  • Avoid lingering or regrouping in runout zones.

Problems

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.

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

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.