Regions
Northwest Coastal.
Another pulse of new snow will be accompanied by strong to extreme winds re-elevating avalanche hazard.
Confidence
Fair - Intensity of incoming weather systems is uncertain
Weather Forecast
A trough of warm air aloft will linger over the region Wednesday before a series of fronts hits the North Coast forcing the arctic air to retreat north. Wednesday will see 5-20cm of new snow accompanied by strong to extreme southerly winds. An above freezing level may mean freezing rain for lower elevations. Snow will continue through the rest of the forecast period with another 10-20cm on Thursday, and 5-15cm on Friday. Winds will remain strong from the south. Freezing levels will climb through the week reaching 2000m by Friday.
Avalanche Summary
Loose natural avalanches are being reported from steep terrain. While natural slab avalanches appear to becoming less frequent avalanche control on Monday produced slab avalanches up to size 3 on virtually all aspects and elevations. It sounds like a lot of these avalanches ran on mid storm instabilities although some larger results observed on South facing slopes released on the late January crust. Glide cracks were reported from the Shames backcountry on Monday.
Snowpack Summary
A new layer of surface hoar was reported to be developing across the region above the 50 to 100cm of snow that fell during last weeks pineapple express. The storm also brought screaming winds out of the E through SE that formed windslabs in lee features. The late-January crust is thought to be down 50 to 130cm in the south of the region and about half this depth in the north. This crust may have surface hoar on it. The mid-January rain crust and/or surface hoar layer is down over 150cm in the south and has generally become inactive although it may still be a concern in thinner snowpack areas. The November crust/facet combo near the bottom of the snowpack is thought to be generally well bonded but may still be reactive in the far north of the region.
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.