Regions
South Coast Inland.
Wind slabs exist on a wide range of aspects and may be hidden by the most recent snow.
Weather Forecast
THURSDAY: Increasing cloud with light flurries in the evening, moderate to strong northwest wind, alpine high temperatures around -10 C in the north and -6 C in the south.FRIDAY: Flurries easing throughout the day with 5-10 cm of new snow in the south and trace amounts in the north, moderate to strong northwest wind, alpine high temperatures around -8 C in the north and -4 C in the south.SATURDAY: Moderate snowfall with 10-25 cm throughout the day, strong southwest wind, alpine high temperatures around -8 C in the north and -4 C in the south.
Avalanche Summary
No new avalanches were observed in the Coquihalla area on Wednesday, while several size 2 wind slabs (40 cm thick) were triggered with explosives on south-facing slopes in the Duffey area. On Tuesday, a small (size 1) wind slab was triggered by a skier on a small west facing feature in the northern part of the region.Reports from the weekend included numerous small wind slabs releasing with skier traffic on steep treeline and alpine features, as well as a few large (size 2-3) naturally triggered slabs in the northern part of the region (some of which were triggered by cornices).
Snowpack Summary
10-20 cm of new snow sits above a variety of old interfaces, including unconsolidated snow in sheltered areas, scoured and wind loaded snow in exposed areas, and a melt-freeze crust below roughly 1900 m. Storm snow amounts from the past week are roughly 60 cm in the south of the region and about half this amount in the north of the region. About 80-150 cm down in the mid snowpack sits the mid-January crust. It generally shows signs of bonding to the overlying snow but will likely remain sensitive to large triggers - especially in thinner snowpack areas. Large, looming cornices exist, they are fragile, and they demand respect. Cornice falls are very effective triggers for avalanches on the slopes below them.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.