Regions
Northwest Coastal.
Safe travel will require a great deal of caution. Be aware of recent wind loading and the potential to trigger deeply buried weak layers.
Confidence
Fair - Forecast snowfall amounts are uncertain
Weather Forecast
SATURDAY: Should see a slight tapering-off of precipitation during the day, with freezing levels around 800m during the day, and lowering to 500m at night. SUNDAY: Will ramp up precipitation with another 8 to 10 cm of snow at upper elevations. Freezing levels again from 500m overnight to 800m with daytime heating. MONDAY: Is forecast for another 5 to 10 cm of snow. Precipitation will be heavier towards the coast, but the inland portion of the Northwest Coast may see as much as 45 cm of snow at upper elevations for the period Thursday though Monday. Winds moderate to strong from the south west for the forecast period.
Avalanche Summary
No reported avalanche observations from yesterday, but commercial operators reported strong winds in the alpine stripping the new snow down to old crust surfaces and building wind slabs and sastrugi.
Snowpack Summary
New snow will be redistributed by strong south west winds into wind slabs on lee slopes. The March 25th surface hoar / crust layer may now become reactive with the new snow loading This interface has been more reactive recently in the northern part of the region, but has been reported throughout the northwest coastal area. The earlier March facet/crust persistent weakness is now down over a metre and has been producing hard, sudden planar results in snowpack tests.
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.