Confidence
Fair - Due to limited field observations for the entire period
Weather Forecast
Wednesday: Moderate snowfall with 5010cm of accumulation, freezing levels around 700m, and strong southwesterly winds easing throughout the day. Thursday: Moderate snowfall with another 5-10cm of accumulation, or more in the Coquihalla Pass area, freezing levels rising to 800m, or higher in Coquihalla Pass, and moderate southwesterly winds. Friday: Light snowfall with up to 5cm of accumulation freezing levels in valley bottoms but rising throughout the day, and moderate southwesterly winds.
Avalanche Summary
No new avalanche observations have been reported; however, heavy loading from snow and wind on Tuesday likely resulted in natural avalanche activity, particularly on leeward slopes.
Snowpack Summary
The Coquihalla Pass area received 90cm of new snow since Sunday, while the Duffy Lake area got about 50cm. Weaknesses linger within and under this storm snow. Of particular note is surface hoar buried late last week, which is likely well preserved and weak on sheltered open slopes treeline and below. The mid-pack seems to be well settled and strong, and possibly bridging deeper weaknesses. However, it wasn't too long ago when snowpack tests were producing moderate but sudden collapse results on the early November facet/crust combination near the base of the snowpack. Furthermore, favorable slab structure for step-down fractures can contribute to the persistence of this deep weakness.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
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.