Regions
Northwest Coastal.
Watch for touchy wind slabs at all elevations created from strong outflow winds.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
FRIDAY: Increasing cloudiness over the day with light snowfall starting in the afternoon, accumulation 10-20 cm overnight, strong outflow winds, alpine temperature near -10 C, freezing level below valley bottom.SATURDAY: Cloudy with light snowfall, accumulation 5 to 10 cm, light to moderate southerly winds, alpine temperature rising to 0 C but cold in the valleys, freezing level near 1800 m with inversion conditions.SUNDAY: Cloudy with light precipitation, accumulation 5-10 mm, moderate southerly winds, alpine temperature near 4 C but possible cold air in the valleys, freezing level near 2000 m with inversion conditions.
Avalanche Summary
A small naturally triggered wind slab was observed on a southerly aspect on Thursday. More avalanches are likely with continuing strong outflow winds.
Snowpack Summary
The snowpack is variable across the region. Wind slabs and storm slabs are found on some slopes in the alpine and at treeline. Strong outflow winds have formed wind slabs on southerly and southwesterly lee features at all elevations.Up to 45 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. Any of these layers could create a persistent slab problem if new snow, wind-loading or warming change the properties of the slab above.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.