Regions
Northwest Coastal.
Reactive slabs will develop throughout the week as snow accumulates. Be prepared to back off if slopes are getting loaded by fresh snow or wind.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
TUESDAY: 5-15 cm of new snow, strong south winds, freezing level dropping to 700 m.WEDNESDAY: More flurries with 10-20 cm of new snow, strong south winds, freezing level steady at 700 m.THURSDAY: Another 10-20 cm of new snow, strong south winds, freezing level steady at 700 m.
Avalanche Summary
Warm alpine temperatures over the weekend caused a natural cycle of large wet loose avalanches (up to size 2.5) on steep solar aspects throughout the region. Some smaller wind slab avalanches were reported in cross-loaded gullies around Bear Pass.
Snowpack Summary
Surface snow is well settled after a weekend of warm alpine temperatures. Wind slabs are lingering on a range of aspects after strong southerly winds on the weekend and outflow winds last week.Below the most recent precipitation, up to 40 cm recent snow overlies several layers of interest in the upper snowpack. These include crusts, surface hoar and facets. A hard crust with associated facets from mid-December sits deeper in the snowpack, about 60 cm down. These layers have been reactive in recent snowpack tests and could potentially be triggered to release large avalanches.The lower snowpack is generally strong, with the exception of areas around Stewart and further north where a basal crust and facets exist.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.