Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
The arctic ridge of high pressure will remain until Wednesday but is beginning to weaken. A series of weak frontal waves will move into northern BC and will be pushed into the southern interior by the arctic ridge. This will result in light, intermittent snowfall for the next few days. A major change in the weather is expected late Wednesday or Thursday when the arctic ridge breaks down and allows a low pressure system to enter southern BC with a westerly flow.Monday: Mostly cloudy, light snow flurries, treeline temperatures around -15C, moderate NW alpine windsTuesday: A mix of sun and cloud, light snow flurries, treeline temperatures around -10C, moderate NW alpine windsWednesday: Mostly cloudy, light snow flurries, treeline temperatures around -10C, winds switching to SW
Avalanche Summary
No recent avalanches have been reported but incoming field data is still very limited in this region. No natural avalanches have been reported in the North Columbia Monashees/Selkirks since Thursday.
Snowpack Summary
Snowpack depths are likely to be highly variable across the region, with elevation, and in wind-exposed areas. Low-elevation and wind-affected areas likely have a shallow faceted snowpack. While in higher elevation sheltered areas 30-50 cm of recent storm snow overlies a variety of old snow surfaces including surface hoar in sheltered areas and/or sun crust on steep south facing slopes. In many areas the storm snow has yet to settle into a sufficiently cohesive slab. However, when temperatures rise, and we get additional snow, expect this crust/surface hoar interface to become a more dangerous problem. Strong NE winds after the storm caused reverse loading and wind slab formation on SE through W aspects in wind exposed areas. Lower snowpack layers include a surface hoar layer roughly 60cm above the ground and an early season rain crust at the base of the snowpack. While these layers have recently become inactive, residual risk of large, destructive avalanches exists, especially in areas with a thinner snowpack. The October crust can be found in the alpine on north aspects and the early November surface hoar appears to be isolated and drainage specific.
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.
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.