Regions
South Coast Inland.
Incoming storms will drive the avalanche hazard for the next few days. The days for playing it safe and conservative continue!
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
SATURDAY NIGHT: 20 to 30 cm new snow in places like the Coquihalla, I expect a little less further north (e.g. Duffy Lake). Freezing level around 800 m. Moderate southerly winds.SUNDAY: Another 20 to 30 cm new snow. Freezing level around 1700 m. Moderate to strong southerly winds.MONDAY: Continued snow with an additional 15 to 25 cm of snow. Freezing level around 1500 m. Moderate southwesterly winds.TUESDAY: Storm continues with more snow, possible as much as 25 cm. Freezing level steady around 1500 m. Moderate to strong southwest winds.
Avalanche Summary
Explosive control work along the Duffey Lake road on Friday produced avalanches up to size 2.5 running on the weak layer of facets buried 60 to 80 cm below the surface. A remotely triggered size 1.5 avalanche in the Coquihalla Summit backcountry suggests this same layer is a concern there.
Snowpack Summary
Up to 1 m of new snow fell since the storm pattern started last Sunday. Strong southerly winds distributed new snow into variable wind slabs in exposed locations. A crust at or near the surface likely exists up to approximately 1700 m.Below the recent storm snow lies a weak layer, comprising 20-30 cm of low density faceted snow. Initially, the snow did not bond well to this layer. While it's likely gaining strength, field observations show that slab avalanches remain possible on this layer.Near the base of the snowpack, a crust exists that previously had sugary facets. This could potentially still be of concern in high north facing areas in drier parts of the region. Elsewhere, this layer is no longer a concern.
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.