Regions
Northwest Coastal.
Forecast snow amounts vary widely across the region with the more western portions receiving the greatest amounts. If your location receives less than 20 cm Thurs night/Fri, these danger ratings are likely one level too high.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain on Thursday
Weather Forecast
Synopsis: Upper NW flow brings significant snow and wind to the North Coast Friday. Saturday offers a break in the action before another wave of warm air moves in late Sunday.Thursday evening: Freezing Level: Surface Precip: 5-20mm 10/30cm with more coastal locations receiving greater accumulations.Friday: Freezing Level: 200m Precip: 2/5mm 4/10cm Wind: Lht gusting Strong, W Saturday: Freezing Level: 1000m Precip: Beginning Saturday night 10/20mm 20/30cm Wind: Lht gusting Strong, WSunday: Freezing Level: 2000m Precip: 20/40mm Wind: Mod gusting Extreme, SW
Avalanche Summary
Avalanche activity slowed down a bit on Thursday, likely due to the cooler temperatures. Earlier this week numerous size 2-3 avalanches were running naturally and with explosive assistance throughout the region on all aspects with the bulk of the activity occurring on N - SE facing aspects.
Snowpack Summary
Total snowpack depth in the region ranges between 140 - 200cm. A surface hoar/facet combo formed during the early December cold snap is now buried 50 - 80cm below the surface. In some locations this layer rests on an old melt freeze crust. The last storm came in wet & heavy with the freezing level as high as 1500m at times. Strong south and west winds during and just after the last storm resulted in widespread wind slab formation.The mid pack is composed of various faceted layers and crusts. A significant crust/facet combo lingers near the base of the snowpack.
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.