Avalanche Forecast

Archived

Apr 21st, 2021–Apr 22nd, 2021

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Sea To Sky.

Plan your day around avoiding sun-exposed slopes and cornices at peak daytime warming. Wet loose avalanches are possible, especially from southerly slopes and terrain features.

Confidence

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

Weather Forecast

Overnight Wednesday: Mostly cloudy. Light northeast wind and freezing levels dropping to the valley bottom.

Thursday: Mix of sun and cloud. Ridgetop wind light from the northeast. Alpine temperatures near -1 and freezing levels 1500 m.

Friday: A mix of sun and cloud. Light winds from the East. Alpine temperatures near -2 and freezing levels 1500 m.

Saturday: Snow 10-20 cm. Alpine temperatures near -4 and freezing levels 1400 m.

Avalanche Summary

No new avalanche reports in this region since last weekend. In the neighboring South Coast Inland large wet slabs were reported from southerly aspects up to size 3.5 and ongoing wet loose avalanches have occurred up to size 2.

Last weekend, multiple large to very large wet slab avalanches were observed near Whistler, size 2-4. Many of these involved the full depth of the snowpack, running to the valley bottom.

As the weather pattern changes and the temperatures drop, I suspect a decrease in natural avalanche activity. However, solar slopes remain suspect when the sun is shining. It can really pack a punch this time of year, even for short periods of time.

Snowpack Summary

A solid melt-freeze crust exists to the mountain top on solar slopes and up to 2000 m on polar slopes. Above 2000 m on North facing terrain, you may find dry snow and a generally well-settled snowpack. Below treeline elevations, the snowpack has been isothermal but will likely lock up as freezing levels drop.

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.
Back off slopes as the surface becomes moist or wet with rising temperatures.
When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
Keep in mind that wet avalanches can be destructive due to their high density.

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.

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.