Regions
Northwest Inland.
The storm snow will take several days to settle and stabilize. Make conservative terrain choices and have a safe holiday period.
Confidence
Poor - Due to the number and quality of field observations
Weather Forecast
On Thursday, expect mostly cloudy conditions with light scattered flurries. Freezing levels should be near valley bottom with light-to-moderate NW wind in the alpine. The next storm system is expected to reach the coast on Friday morning but it doesn't look like much precipitation will make it into the interior. Friday may see 2-4mm of precipitation with freezing levels around valley bottom and light-to-moderate SW wind in the alpine. Saturday may see another 3-6mm with temperatures remaining cold and alpine winds easing.
Avalanche Summary
On Tuesday we received a report of a size 1.5 skier remotely triggered avalanche in the far north of the region. It released on a steep, wind loaded feature and was triggered from 5m away. The slab was 25-45cm thick and occurred around 1600m elevation. On Sunday we received a report from the Hankin area of a natural size 1 slab avalanche. This occurred on a north aspect at treeline. The crown depth was around 20cm and it failed on the most recent rain crust. Check out the report here: https://goo.gl/WdmvxL
Snowpack Summary
Since Friday, the region has received around 30-50cm of new snow. Strong winds have created wind slabs in exposed terrain and have probably striped the snow off of exposed slopes. Below the new snow you'll likely find old wind-scoured surfaces or old wind slabs in exposed terrain, and settled storm snow closer to treeline. Near the base of the snowpack, weaknesses such as the mid-November crust-facet layer are still of concern. We don't know much about this layer but older reports suggest that it may still be reactive in isolated areas.
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.
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.