Regions
Northwest Coastal.
Weather Forecast
Thursday: Heavy precipitation with up to 60mm expected. Extreme southerly winds and freezing levels as high as 1200m. Friday and Saturday: Light to moderate precipitation continues throughout the period, with some breaks, all in a moderate southwest flow.
Avalanche Summary
Warm temperatures and light to moderate precipitation resulted in several low-elevation natural storm slab avalanches up to Size 2. Explosive control on Tuesday produced numerous 40-60cm thick wind slab avalanches up to Size 2.5 with wide propagation on all aspects in the alpine. Several 100-150cm thick slab avalanches up to Size 3.5 were also triggered.
Snowpack Summary
Total snowpack depths are at new record levels for this time of year. Recent warm temperatures helped settle storm snow into a touchy surface slab at lower elevations. Other weaknesses within and under (Jan. 20th facets) the 150+cm of recent storm snow create the potential for step-down avalanches, but things seem to be settling rapidly. Strong winds associated with recent storms means large weak wind slabs and cornices on lee and cross-loaded terrain. Most snowpack concerns are limited to the surface layers, however large triggers such as cornice falls and smaller avalanche stepping-down could affect deeper weaknesses.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
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.