Avalanche Forecast

Archived

Apr 21st, 2019–Apr 22nd, 2019

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Sea To Sky.

Flurries and wind will build thin, reactive deposits through the day and may hide recently formed wind slabs, use caution around cornices and lee terrain. Loose wet avalanches remain a concern, travel early and avoid moist/wet slopes.

Confidence

Moderate -

Weather Forecast

SUNDAY NIGHT: Cloudy with flurries, trace to 5 cm, moderate south-southwest wind, alpine temperature -2 C, freezing level 1500 m.

MONDAY: Wet flurries and alpine snow, 5-15 cm snow, moderate southwest wind, alpine temperature 0 C, freezing level 2100 m.

TUESDAY: Cloudy with isolated flurries up to 8 cm by morning, light to moderate west-southwest wind, alpine temperature +1 C, freezing level 1800 m.

WEDNESDAY: Mix of sun and clouds, light southwest wind, alpine temperature +2 C, freezing level 2000 m.

Avalanche Summary

On Saturday morning around the Whistler Backcountry, a natural wet loose avalanche cycle to size 2 was observed on all aspects from 1900-2200m. Wet slab avalanches to size 3 were observed on loaded northerly features in the alpine. Natural cornices failures to size 2 were also observed and explosives triggered cornices size 2-2.5. Further south in the region, cornices failing naturally triggered large (up to size 3) slab avalanches on the slopes below.

On Friday morning, explosives triggered two wet loose size 2 avalanches and several size 2 cornices, in some cases cornices triggered wet slab avalanches to size 2 on the slopes below. One natural storm slab avalanche was observed on a north aspect, the likely trigger a natural cornice failure on the slope.

On Thursday night and into Friday, a loose wet avalanche and cornice cycle occurred in the region during the storm, producing small to large avalanches (size 1 and 2). Most of the avalanches occurred in the alpine as well as treeline.

Snowpack Summary

Recent snow and rain, coupled with warm temperatures and rising freezing levels produced a natural avalanche cycle over the weekend. A crust has developed on most slopes except for high alpine polar aspects where up to 10 cm loose, dry snow is holding on. Cornices and wind slabs have developed with recent strong south winds. The snowpack below treeline is saturated and rapidly melting.

Spring is upon us and the snowpack can change drastically in a short time with solar or temperature input. This MIN report here provides a good summary of aspect and elevation-dependent conditions around the Whistler Backcountry on Saturday.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.