Regions
Northwest Coastal.
Spring Conditions. The ridge of HIGH pressure is breaking down and a weak storm is moving on-shore from the south. High daytime freezing levels will continue the cycle of wet slab and loose wet avalanches.
Weather Forecast
Clear overnight with freezing levels near 2000 metres and moderate southerly winds. High cloud developing Thursday morning with freezing levels rising up to about 3000 metres. Winds becoming easterly in the afternoon as the cloud increases and light precipitation begins to fall. Freezing levels dropping to 2000 metres by Friday morning with light precipitation and light easterly winds. Freezing levels dropping to 1500 metres on Saturday with 5-15 cm of new snow expected in the alpine.
Avalanche Summary
Some thin wind slab avalanches were released by explosives in the north of the region near Stewart. I suspect that recent wind slabs have settled out and either released naturally in the sun or have melted and re-frozen into the spring snowpack. There are not may commercial operations still working in the field, so data is sparse at this time of year. If you have observations from your travels, please consider sharing through the MIN (Mountain Information Network).
Snowpack Summary
Overnight cooling has formed a new surface crust on all aspects above 1000 metres. Daytime heating continues to melt the surface snow on all aspects. Recent wind slabs are suspected to have settled out due to the high temperatures and strong solar. There is about 40 cm of moist snow above the early April melt freeze crust in the Stewart area. This buried crust may act as a sliding layer for wet slab avalanches. Large wet slab avalanches may step down to the ground or gouge down to the ground in their tracks. Cornice falls and loose wet avalanches are likely during periods of strong solar radiation and high daytime freezing levels. Travel early before crusts break down, and monitor crust thickness and strength throughout the day.
Problems
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.
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.