Stormy conditions continue this week. Expect fresh soft slabs to build, especially in wind exposed terrain.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Tuesday
Weather Forecast
TUESDAY: Periods of snow – around 15 cm. The freezing level is around 800-1100 m. Ridge winds are moderate from the south. WEDNESDAY: Possible sunny breaks to start with snow developing late in the day. The freezing level could rise to 1200-1400 m. Ridge winds are light but increase to strong from the SW-SE with the arrival of the storm. THURSDAY: Cloudy with sunny breaks and a chance of flurries. The freezing level is near 1400 m and winds are light.
Avalanche Summary
Backcountry observations have been limited, likely because of inclement weather, but there were reports of a few natural and skier controlled or accidentally-triggered slab avalanches up to size 2 on Sunday. Of note, an isolated yet destructive size 3 natural persistent slab avalanche was reported late last week in the South Chilcotin area north of Goldbridge. The avalanche failed on surface hoar buried in early February. Cornices are large and fragile, and may also fail under the weight of a person.
Snowpack Summary
Storm totals from the past week were between 50-70cm with more currently falling and much more on the way this week. Previous strong southwesterly winds have shifted the new snow into deeper storm slabs on lee and cross-loaded alpine and treeline features. On all but higher elevation shaded slopes the new snow from Sunday likely overlies a melt-freeze crust from high freezing levels and sun on Saturday afternoon. Below the recent storm snow, the snowpack is generally strong and well-settled. That said, a layer of surface hoar buried at the beginning of February is a concern in the South Chilcotin area and can be found about 70cm below the surface. Although this layer is isolated, it has been responsible for destructive natural avalanche activity and is worth keeping on your radar if you're headed to the north of the region.
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.