Regions
Northwest Coastal.
Highly sensitive storm slabs are everywhere. Conservative terrain selection is essential for safe travel.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
Tuesday: Mainly cloudy with another 10-15cm of snow, moderate southerly winds and freezing levels around 500m. Wednesday: A mix of sun and cloud with isolated light flurries bringing 2-5cm, moderate to strong southeasterly ridgetop winds and freezing levels as high as 700m. Thursday: As much as 15-20cm expected for immediate coastal areas, but dryer inland. Strong southerly winds and freezing levels around 500m.
Avalanche Summary
Reports from Sunday include several skier, vehicle and explosive triggered 20-60cm thick (or thicker where wind-loaded) slab avalanches up to Size 2. These slabs were both directly and remotely triggered and ran on surface hoar buried on (or around) January 9th at all elevations and on all aspects.
Snowpack Summary
Recent storm snow amounts have been variable across the region, but generally 30-45cm since mid January when the most recent surface hoar was buried. Below that is another surface hoar layer down 50-65cm. Both are showing a high propensity for propagation with remote triggering and whumpfing, as well as sudden shears with snowpack tests in the easy to moderate range. Deeper persistent weaknesses buried in December have the potential to wake-up to heavy loading, rapid warming, or avalanches stepping-down. Recent strong to extreme southeast winds have loaded leeward features on west through north aspect slopes.
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.