Confidence
Fair - Forecast snowfall amounts are uncertain on Saturday
Weather Forecast
Synopsis: A weakening upper trough stalled off the southern BC coast should continue to deliver light snowfall Saturday night and scattered very light snowfall on Sunday. Look for gradual clearing on Monday.Saturday Night: Precipitation: 1 - 6mm | 2 - 10cm; Wind: Treeline: Light, SW | Ridgetop: Moderate, SWSunday: Freezing Level: 1100m - 1200m; Precipitation: 0 - 2mm | Trace; Wind: Treeline: Light, SW | Ridgetop: Light, SWMonday: Freezing Level: 1300 - 1600m; Precipitation: Nil; Wind: Treeline: Light, SW | Ridgetop: Light, WTuesday: Freezing Level: 1200 - 1700m Precipitation: Nil; Wind: Treeline: Light, Variable | Ridgetop: Light, NW
Avalanche Summary
On Friday small pockets of wind slab were sensitive to human triggering. I suspect activity ramped up Friday night into Saturday.
Snowpack Summary
New snow accompanied by strong southerly winds has likely formed fresh sensitive wind slabs in wind exposed terrain, and storm slabs that extend down into the treeline vegetation band. This snow adds additional load to the mid March surface hoar / crust interface, now down 80 - 110cm. The bond at this interface is improving, but it may still be sensitive to human triggering. The early-March crust/facet layer is down about 100-150 cm and the early February layer is now down close to 200 cm. These layers are largely dormant at this time.The lower snowpack is strong and well settled.
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.