Regions
Northwest Coastal.
When the sun comes out on Wednesday, expect lots of solar triggered sluffing on steep slopes. New wind slabs are expected to be reactive in leeward features in the alpine.
Weather Forecast
A mix of sun and cloud is expected for Wednesday but light flurries may continue in the morning. Light southerly winds are expected in the alpine and afternoon freezing levels should be around 1400m. Mostly sunny conditions are expected Thursday morning with increasing cloudiness in the afternoon. Winds should remain light most of the day and afternoon freezing levels are expected to be around 1600m. Light snowfall is expected on Friday. Alpine winds are forecast to be moderate to strong from the southwest with afternoon freezing levels around 1300m.
Avalanche Summary
On both Sunday and Monday, loose wet avalanches up to size 2.5 were reported in the far 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 Wednesday, newly formed wind slabs are expected to be reactive to human-triggering in the alpine. Widespread solar triggered loose sluffing is expected with the new snow sliding on the firm crust layer. Cornices have been weak recently and may fail naturally with storm loading.
Snowpack Summary
Prior to the new snowfall, dry winter snow was being reported on northern aspects above 1700m in the area north of Stewart. South aspect slopes and lower elevations were undergoing daily melt-freeze cycles. Around Terrace, melt-freeze conditions were reported at all elevations. The new snow will bury this crust and strong southerly winds in the alpine will build wind slabs. The region should return to melt-freeze conditions on Wednesday with surface crusts forming overnight and breaking down during the day. The snowpack's strength is directly related to the thickness and strength of these surface crusts. 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
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.
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.