Regions
South Coast Inland.
The new snow and strong wind is expected to form new wind slabs that will bury the rain crust. If more than around 30 cm of snow accumulates in your riding area, a more widespread storm slab problem may develop and local hazard could be High.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Thursday
Weather Forecast
Light snowfall is expected Wednesday overnight with another 10-20 cm in the forecast. Unsettled conditions are expected on Friday with the potential for another 5-10 cm as well as sunny breaks. Freezing levels are expected to be around 600 m early Thursday morning and reach around 1000 m or so in the afternoon. Alpine wind is forecast to be moderate to strong from the southwest for most of the day. Light intermittent snowfall is forecast to continue Thursday overnight and during the day on Friday with the potential for another 5-15 cm as well as sunny breaks. Freezing levels are forecast to remain below 1500 m during this period and alpine wind should remain moderate to strong from the south and southwest. The last significant storm pulse is currently forecast for Saturday with 20-40 cm currently forecast during the day. Amounts are expected to be greatest in the south of the region.
Avalanche Summary
Observations were limited on Tuesday but reports from the north of the region include isolated natural wet avalanches and ski cutting triggering size 1 loose wet avalanches. On Monday, numerous loose wet avalanches up to size 2 were observed in the Coquihalla area. In the north of the region on Monday, three natural size 1.5-3 cornice releases were observed on north and northeast aspects. Also in the north, a skier triggered a size 1 storm slab in a loaded alpine feature and a skier triggered a size 1 persistent slab on an east aspect at 1800 m which released down 40 cm on the late February surface hoar layer.On Thursday, the new snow should be burying a widespread crust and is expected to form new wind slabs in exposed terrain. It has become difficult to trigger the February weak layers but there is still a chance that smaller wind slab avalanches or a cornice fall could still step down and release a persistent slab avalanche. At lower elevation, continued rain may result in wet sluffing from steep terrain features.
Snowpack Summary
On Tuesday, freezing levels reached at least 2100 m. In the Coquihalla, rain has been reported to the mountain tops. As temperatures drop over the next couple days, a widespread crust is expected to form and the snowpack is expected to gain considerable strength. New snow on Thursday will accumulate over this crust and strong wind is expected to form new wind slabs.In the north of the region, the February weak layers are now down 80-120 cm. The layer of buried surface hoar has recently produced a few persistent slab avalanches. The crust/facet layer appears to be gaining strength but may also still be reactive in isolated areas. In the Coquihalla area, the crust/facet layer is down well over 1 m and appears to have gone dormant.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
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.