Regions
Northwest Coastal.
Hazard could be higher than forecast on solar aspects in the afternoon. Cornices are growing large, and scary-looking and require careful consideration.
Confidence
Fair - Forecast snowfall amounts are uncertain on Monday
Weather Forecast
Synopsis: The high pressure ridge in the interior of has cooled things down a bit, but will recede with the oncoming Pacific frontal system.Tonight: Cloudy, no precipitation in the forecast, freezing level around 100 metres, winds light to moderate, from the north west.Monday: Cloudy with flurries. Forecast models differ on precipitation amounts for Monday night freezing level around 400 metres, winds light to moderate from the north. .Tuesday: Cloudy with a trace of precipitation in the forecast, freezing level at 600 metres, winds light, from the north.Wednesday: Cloudy with isolated flurries, trace of precipitation in the forecast. freezing level around 600 metres, light ridge top winds.
Avalanche Summary
No reports of avalanche activity in the forecast region from yesterday. Remember that the weak layers are still there, and rider triggering is still possible. Cornices have become quite large in some parts of the forecast region and they are definitely something to watch out for.
Snowpack Summary
The area has received 75 to 150cm of snow over the past 5 to 7 days. The recent storm snow arrived with strong winds and produced wind slabs at tree line and above and increasing the depth on the slab that now overlies the March persistent weak layer. In addition, much of the recent storm snow has fallen on a melt freeze and/or rain crusts that exist in most parts of the region below 1200 metres. This will most likely become reactive on solar aspects when the sun finally comes out.The March weak layer is a combination of hard wind-scoured slab surfaces in exposed terrain, facets and/or surface hoar in sheltered and north aspects, and sun crust on steep solar aspects. This layer is widespread throughout the forecast region and is now buried close to 150cm in most parts of the area. A late January/early February crust/facet/surface hoar combo is still showing up in snowpack tests with moderate to hard shear tests. It appears to be dormant for the time being, but a sudden increase in load, a cornice failure, or a large rainfall event could "wake up" this layer and result in a large destructive avalanche.
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.