Avoid avalanche terrain on Tuesday. The new snow will need time to settle and gain strength.
Weather Forecast
MONDAY NIGHT: Heavy snowfall with accumulations of 20-30 cm, 30-60 km/h southwest wind, treeline temperatures around -2 C, freezing level around 500 m.TUESDAY: Snow continues in the morning with another 5-10 cm then eases off in the afternoon, total accumulation of 30-45 cm over the course of the storm, 20-30 km/h northwest wind as the storm eases, treeline temperatures near -2 C, freezing level 800 m.WEDNESDAY: Mix of sun and cloud, light northwest wind, treeline temperatures near -2 C, freezing level 800 m.THURSDAY: Cloudy with isolated flurries, 30-50 km/h southwest wind, treeline temperatures near +1 C, freezing level 1200 m.
Avalanche Summary
Avalanche activity over the weekend was limited to small slab and loose avalanches in the top 20 cm of snow (size 1). Looking ahead, the most likely problem will be fresh storm slabs, however the lingering persistent weak layer in the North Shore Mountains still poses a low likelihood - high consequence problem.
Snowpack Summary
30-45 cm of new snow will be accompanied with strong southwest wind. The new snow is falling on a sun crust on steep southerly slopes, and possibly on weak surface hoar crystals on sheltered and shaded slopes. The combination will form very touchy storm slabs on Tuesday.A layer of weak and sugary faceted grains sits on a melt-freeze crust about 50 to 120 cm deep. The layer is likely most prominent in the North Shore Mountains and on north aspects. This layer continues to be reactive in snowpack tests. The problem is not typical for the region and we expect this persistent weak layer to continue to linger.The lower snowpack is generally strong.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.