Regions
Northwest Coastal.
Avalanche danger rising to HIGH as the storm slab continues to develop.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Entering a very stormy period for the North Coast. Very strong Southerly winds overnight and during the day on Saturday. 15-25 cm of snow tonight above 600 metres elevation. Another 15-25 cm during the day on Saturday as freezing levels rise up to at least 1000 metres and maybe as high as 1400 metres in some areas. Winds decreasing to strong by Sunday morning with another 10-15 cm expected and a further 10-15 cm during the day. Monday should be drier with Westerly winds and dropping freezing levels.
Avalanche Summary
No new avalanches reported. The forecast new storm is expected to increase avalanche activity over the next few days.
Snowpack Summary
A new storm slab is developing above the recent mix of surfaces which include wind slabs in alpine terrain, hard rain crusts at lower elevations and weak surface hoar crystals. Last week's heavy rain affected southern parts of the region up to alpine elevations, while the far north remained drier and generally has a weaker snowpack. Areas which previously received rain have probably now formed a hard frozen crust. Upper elevation terrain and far northern areas are likely to have wind slabs and large fragile cornices. Deeper in the snowpack, weaknesses such as the mid-November crust-facet layer still exist. Avalanches at this interface have become unlikely, although the consequences of a release remain high. This layer may be more sensitive to triggering in steep, unsupported high alpine terrain, or 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.