Danger could rise sooner than indicated if we see more than 10 cm of new snow (with wind) before the end of the day on Wednesday.
Weather Forecast
WEDNESDAY: Mainly cloudy with snow developing late in the day. The freezing level should be around 1500 but will rise to 1800 m overnight. Ridge winds increase to strong or extreme from the S-SW with the arrival of the storm. THURSDAY: Periods of snow – 20-50 cm Wednesday night through Thursday. The freezing level drops to around 1400 m and winds are moderate to strong from the south. FRIDAY: Cloudy with sunny breaks. The freezing level could rise to 1800 m during the day and winds ease to light.
Avalanche Summary
Explosives control on Monday in the Northwest corner of the region produced a few size 3 slabs that released on the Feb. 11 crust. On Monday, there were also reports of widespread evidence of a large natural avalanche cycle (up to size 3) that probably occurred on Saturday or Sunday. Cornices have also been popping off with some regularity.
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.