Storm snow amounts will vary across the region. The Coquihalla will see higher amounts then the Duffy. Avoid avalanche terrain.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Thursday
Weather Forecast
Thursday: 15-30 cm overnight Wednesday at upper elevations, with the higher accumulations being in the southern part of the region. 5-15 cm Thursday morning tapering off by early afternoon. Ridgetop winds strong from the southwest. Alpine temperatures near -5 with freezing levels 1300 m. Friday: Mix of sun and cloud with alpine temperatures near -8 and freezing levels at valley bottom. Ridgetop winds light from the north. Saturday: Mostly clear with no forecast snow. Alpine temperatures near -10 and ridgetop winds light from the northeast.
Avalanche Summary
On Tuesday, no new avalanche observations were reported from the northern part of the region (Duffy). In the south (Cascades) numerous glide avalanches up to size 3 were reported. Glide releases have a higher likelihood of failing when the ground cover is smooth bedrock or grass. Other avalanches to note from the south include wet slab avalanches up to size 2.5 with one reported as a size 3 from a steep southeast slope near 1700 m. Natural avalanches are likely with forecast storm snow, rain at lower elevations and strong ridgetop winds.
Snowpack Summary
Recent snowfall totals are highly variable. In the south, up to 20 cm of new snow fell bringing the alpine totals up to 40 cm since the weekend. In the north, new snow totals are half that and rapidly decreasing below 1800m. This new snow sits on old wind slabs in alpine locations and has buried a crust at treeline. At lower treeline and below elevations, warm temperatures (and rain in many locations) have created heavy snow conditions. This new snow adds to the 80-150 cm mid pack that sits above the mid- January crust, which generally shows signs of bonding. I would still remain suspect of this deeper layer, especially now, with additional load stressing the snowpack. Large fragile cornices could also act as a trigger on the slope below.
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.