Regions
South Coast Inland.
Fresh storm slabs will be reactive to human-triggers, especially in wind-affected terrain.
Weather Forecast
SUNDAY: Gradual clearing and cooling as Arctic air pushes into the region, moderate to strong northeast wind, alpine high temperatures around -18 C in the north and -12 in the south.MONDAY: Sunny, moderate northeast wind, alpine high temperatures around -15 C.TUESDAY: Mostly sunny, light wind, alpine high temperatures around -12 C.
Avalanche Summary
Preliminary reports from Saturday include small dry loose avalanches in steep terrain in the Duffey area. No reports have come in from the south of the region, but natural slab activity was likely given the intense snowfall. Wind slabs activity has been reported in northern parts of the region over the past week, including a size 2 skier-triggered avalanche in a cross-loaded gulley feature at treeline on Friday.
Snowpack Summary
Saturday's storm delivered ample snow to the region, with the Duffey area receiving at least 30 cm and Coquihalla receiving 40-50 cm. To the north, the storm snow is primarily low density with the exception of exposed terrain where wind has formed slabs. To the south, the snow is likely denser and formed a more widespread slab.A few interfaces buried last week could potentially support wide propagations in the storm slabs. These include scoured crusty surfaces on south-facing alpine slopes, a melt-freeze crust up to 1700-1900 m, and hard wind damaged snow in exposed terrain.The mid-January crust is now buried beneath 80-150 cm of settled snow and may remain sensitive to large triggers - especially in thinner snowpack areas in the north part of the region. 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
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.
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.