Regions
Northwest Inland.
Forecast new snow and wind are expected to increase the avalanche danger.
Confidence
Fair - Forecast snowfall amounts are uncertain on Tuesday
Weather Forecast
Overnight and Tuesday: Some Pacific moisture (3-5 cm) is expected to push into the Northern coastal areas and then slide inland. Mostly overcast with light precipitation, cold alpine temperatures, and moderate to strong Southwest winds. Freezing levels at about 500 metres.Wednesday: Overcast with light precipitation and light winds. Freezing level about 500 metres and alpine temperatures around -15.Thursday: Overcast with a chance of sunny breaks in the afternoon. Light Easterly winds and temperatures around -15 in the alpine.
Avalanche Summary
No new reports of avalanches since the Silverking involvement on Saturday. The storm slab continues to be a concern for triggering from light additional loads. Long fracture propagations and triggering from adjacent terrain are likely.
Snowpack Summary
There has been 40 - 65 cm of new snow in the past week in parts of the forecast region. That, combined with strong winds, continues to build wind slabs in lee terrain and increase the depth of the storm slab that overlies the persistent weak layers. A rain crust has formed at lower elevations, typically below 1200 metres. Solar aspects have been reported to be moist to ridgetops, and may have a crust with new snow on top of it. The March weak layer is a combination of wind pressed snow, facets and/or surface hoar in sheltered and north aspects, and sun crust on steep solar aspects and is widespread throughout the forecast region. this layer is now buried well over a metre in some parts of the region. A late January/early February crust/facet/surface hoar combo is still showing up in snowpack tests with moderate to hard shear tests. This layer will be with us for a long time, and a slide triggered on this layer could be very large and destructive.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.