Regions
Northwest Coastal.
A brief return to winter in the alpine for Tuesday. New snowfall and strong southerly winds are expected to form new wind slabs at higher elevations.
Weather Forecast
A weak storm system is expected to reach the coast Monday overnight. 5-15cm of snowfall is forecast with the greatest amounts along the coast. Strong southerly winds are expected in the alpine with afternoon freezing levels around 1300m. Light snowfall may continue Tuesday overnight and should be done by Wednesday morning. A mix of sun and cloud is forecast for Wednesday with light alpine wind and afternoon freezing levels around 1400m. Thursday is forecast to be mainly cloudy with sunny breaks, light alpine wind, and afternoon freezing levels around 1500m.
Avalanche Summary
On Sunday afternoon, loose wet avalanches up to size 2.5 were reported in the north of the region. With the arrival of spring, field observations and data have become quite limited in the region. A lack of avalanche reports does not mean avalanches are not occurring. On Tuesday, new wind slabs are expected to form in the alpine. Cornices have been weak recently and may fail naturally with storm loading. Loose wet avalanches are possible at lower elevations that see rainfall.
Snowpack Summary
Dry winter snow is being reported on northern aspects above 1700m in the area north of Stewart. South aspect slopes and lower elevations are most likely undergoing daily melt-freeze cycles. Around Terrace, melt-freeze conditions are being reported at all elevations. Surface crusts are forming overnight and breaking down during the day. The snowpack's strength is directly related to the thickness and strength of these crusts. Where layers remain in the snowpack, they are generally bonding. A widespread crust/facet layer from early February and depth hoar at the bottom of the snowpack (primarily in northerly & inland areas) are dormant. Cycles of melting and refreezing have limited the reactivity of these old layers. However these layers, or the ground, could potentially once again be the layer for an isolated yet large avalanche with prolonged periods of warming.
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.
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.