A rapid shift to warm, sunny conditions will increase the range of avalanche problems as well as their potential for reactivity.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
Thursday: A mix of sun and cloud with thicker valley cloud due to an alpine temperature inversion. Light west winds. Freezing level to 3300 metres with alpine temperatures of +4. Cooler at lower elevationsFriday: Sunny at highest elevations with valley cloud due to lingering temperature inversion. Light west winds. Freezing level to about 3200 metres with alpine temperatures of +2. Cooler at lower elevations.Saturday: Mainly sunny at highest elevations with continued valley cloud. Light southwest winds. Freezing level to 3300 metres with alpine temperatures of +3. Cooler at lower elevations.
Avalanche Summary
Reports from Tuesday included several observations of wind slabs releasing to Size 2 in the Fernie area. These were mainly triggered with explosives but one Size 1.5 slab did release with skier traffic. Looking forward, forecast sunshine and warm temperatures may have the greatest destabilizing effect where more recent reverse loading and crossloading has occurred at higher elevations. Please submit your observations to the Mountain Information Network (MIN).
Snowpack Summary
Recent shifting winds have been redistributing loose snow at higher elevations, crossloading and forming wind slabs on a wide range of aspects at treeline and above. Below the surface, 40-60 cm of accumulated storm snow now sits above the crust that formed a week ago. The buried crust is supportive and approximately 30 cm thick. It extends from 1600 m to mountain top elevations on all aspects. The bond of our recent storm snow to this crust is expected to be strengthening and it has produced hard, resistant results in recent snowpack tests. Below this interface, the snowpack is moist to ground. The average snowpack depth at treeline is 60-80 cm while a deeper snowpack exists in the alpine.
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.