Regions
Northwest Coastal.
The effect of recent warming is uncertain, and buried weak layers exist in the snowpack. Conservative terrain selection remains critical.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Wednesday
Weather Forecast
Wednesday: 5-15cm of new snow / Strong southwest winds / Freezing level at about 1100mThursday: 4-8cm / Light and variable winds / Freezing level at about 1100mFriday: Light flurries / Light and variable winds / Freezing level at about 800m
Avalanche Summary
Over the past few days a natural avalanche cycle up to size 3 occurred in response to heavy snow and wind. The peak of the natural avalanche activity occurred a few days ago; however, human triggered slab avalanches to size 1.5 were observed failing on recently buried surface hoar as recently as Monday. Recent naturally triggered wind slabs were also observed.Ongoing storm slab activity is expected in response to new snow and wind on Tuesday and Wednesday. New snow will also add stress and destructive potential to deeper weak layers. Loose wet avalanches are expected to continue at lower elevations where precipitation falls as rain.
Snowpack Summary
Anywhere from 40-80 cm of recent snowfall has fallen. Precipitation has been falling as wet snow or rain at lower elevations. The new snow overlies a variety of old surfaces which include wind slabs, facets, sun crusts on steep solar aspects and well-developed surface hoar in sheltered locations. Deeper in the snowpack, the mid-January surface hoar/facet layer is now down roughly 80-120 cm. Recent observations suggest the layer has generally stabilized but isolated weaknesses may still exist, mainly where buried surface hoar is still intact. Below this layer, the snowpack is generally strong and well settled. The exceptions are areas around Bear Pass and Ningunsaw where basal facets remain an ongoing concern, especially in shallow snowpack areas.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.