Regions
Northwest Inland.
The hazard may be higher than expected on solar aspects if the sun comes out and the temperature goes higher than forecast. Pay careful attention to cornice hazard.
Confidence
- Intensity of incoming weather systems is uncertain
Weather Forecast
Synopsis: A weak frontal system will pass through the area today and will be followed by a short-lived high pressure ridge.Tonight: Cloudy with clear periods, trace of precipitation in the forecast, freezing level at valley bottom, winds light, from the south west.Saturday: Cloudy with snow, 5 to 10cm of precipitation, freezing level around 300 metres, ridge top winds should be light from the south east.Sunday: Cloudy periods, trace of precipitation in the forecast, freezing level around 900 metres, light ridge top winds from the south east.Monday: Cloudy with snow flurries, 10 to 15cm precipitation, freezing level around 600 metres, winds light to moderate from the north.
Avalanche Summary
Some reports of natural avalanche activity in steep terrain, a few large heli-remotes and natural cornice failures producing large avalanches With continued loading and wind, rider triggering is definitely possible at this time.
Snowpack Summary
15 to 30cm of precipitation in the past week in some 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 moist to ridgetops, and may have a crust with new snow on top of it. The solar aspects may become reactive when the sun comes out.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 would be very large and destructive. Recent warming temperatures will be good for bonding on this layer, but a sudden increase in load, or a large rainfall event could "wake up" this layer and result in very large avalanches.
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.