Regions
Northwest Coastal.
Potential for a cold, windy day. Watch for building wind slabs, even at low elevation.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
THURSDAY: Cloudy with strong outflow winds. Flurries possible. Alpine temperature near -20.FRIDAY: Clear with light winds. Flurries possible. Alpine temperature near -20.SATURDAY: Cloudy with light winds. 5-10 cm snow. Alpine temperature near 0, but cold in the valleys.
Avalanche Summary
A natural storm slab cycle to size 2 was reported to have run during the storm last Monday. Skiers near Shames reported sluffs running far on Monday. A skier triggered a size 2 wind slab on Sunday on a NW aspect at about 1400 m near Terrace.
Snowpack Summary
The snowpack is variable across the region. Wind slabs and storm slabs may be found on some slopes in the alpine and at treeline. 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.