The snowpack is touchy and primed for human-triggered avalanches. Don't let the improving weather lure you into high risk scenarios.
Confidence
Fair - Intensity of incoming weather systems is uncertain
Weather Forecast
High pressure building off the coast and pushing north will be responsible for a cooler and dryer NW flow. Some unstable disturbances are embedded in this flow, bringing scattered cloud and light precipitation. Models disagree with timing and precipitation amounts.Saturday: Mix of sun and cloud. Light snow possible. Alpine temperatures near -12.0. Light NW ridgetop winds.Sunday: Cloudy with sunny periods and trace snow amounts. Alpine temperatures near -21.0. Ridgetop winds moderate from the North.Monday: Sunny. Alpine temperatures near -22.0. Ridgetop winds blowing light from the north.
Avalanche Summary
On Friday, the SR field team witnessed several large snowmobile remote triggered slab avalanches in the Elk Valley North. These avalanches were all triggered below treeline around 1800 m. On Thursday, a natural size 2.5 avalanche occurred near the Coal Creek road. The debris just reached the road, didn't block it but the air blast covered the road with branches. On Wednesday, there was a size 4.0 natural slab avalanche in the neighbouring Lizard range that ran full path and piled up debris including mature timber in the valley bottom. Wind loading and sunshine are expected, natural avalanche activity may pick up; however, conditions are primed for human triggered slab avalanches.
Snowpack Summary
Up to 15 cm of new snow fell on Friday, adding to the recent storm snow that is close to a metre thick. This slab continues to settle and become more cohesive, overlying a complex medley of persistent weak layers (mainly facets and some surface hoar). This weak layer is below the storm slab and widespread on all aspects and at all elevations across the region. This is the classic firm slab over soft and weak layer that allows for wide propagations and remote triggering. This problem may persist for days after the storm or even weeks. Wind loading and sunshine may cause another natural avalanche cycle on this layer. The mid snowpack is strong and supportive. A deep persistent layer of facets and depth hoar near the base of the snowpack has remained dormant to this point, but may become a concern with additional load and stress on the snowpack.
Problems
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.
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.