The trees are NOT a safe haven right now as a persistent weak layer at lower elevations remains sensitive to human triggers. Snow and wind from the weekend storm will likely form touchy storm slabs in wind exposed terrain at upper elevations too.
Confidence
Low - Due to the number of field observations
Weather Forecast
A tightly wound and rapidly deepening low pressure centre is expected to track just south of Vancouver Island Saturday afternoon. The northern edge of this system should track through the Cariboos Saturday night with lingering convection generating continued snowfall through the day Sunday. A ridge is expected to take over the pattern Monday afternoon and should persist through Wednesday. SATURDAY NIGHT: 2 to 8cm of snow, freezing level at valley bottom, strong SW winds. SUNDAY: 1 to 8cm of snow, freezing level near valley bottom, moderate SW winds. MONDAY: Trace of snow, freezing level at valley bottom, light W/NW winds. TUESDAY: 1 to 5cm of snow, freezing level at valley bottom, moderate winds generally out of the west.
Avalanche Summary
Recent observations have been very limited, but I suspect that recent avalanche activity is far more widespread than the current data set would lead us to believe. The last significant observation was from Thursday when a large natural avalanche (size 2.5) was observed on a NE facing feature at 2000m.
Snowpack Summary
A string of storms between December 2nd and December 11th produced 70 - 130cm of storm snow in the Cariboos which is settling out at all elevations. You may find a brittle crust about 10 to 30cm below the snow surface as high as 2000m that was formed by rain and warm temperatures last Tuesday. Below all the new snow lies the early December persistent weak layer. This weak layer manifests as an old sun crust on due south facing features in the alpine, large grained surface hoar below 1800m and small facets in isolated pockets. The surface hoar is the major player and it's been most reactive below treeline between 1400 and 1800m. Recent winds out of the south and southwest have formed wind slabs on lee features that are mainly confined to the alpine, but you may find the odd fresh wind slab at treeline too. The mid and lower portions of the snowpack are thought to be well settled.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.