A big change in the weather is headed our way. Tuesday is the probably going to be the last day you can confidently get after it in big terrain for a while.
Confidence
Poor - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Bottom Line: The weather is changing, the inversion should be cleared out by Tuesday morning. The coast will likely get hammered as a digging upper trough makes landfall over the next few days. Some of the snow and southerly winds associated with this event are expected to spill over into the Southern Columbias. At this point amounts and timing are too dynamic to pin down, but the region should see 2 to 15cm of snow Tuesday night, with an additional 5cm Wednesday. Strong SW winds are expected throughout the region beginning Tuesday night. The freezing level should remain at valley bottom until Thursday when its expected to climb to around 1500m. For detailed mountain weather information visit: avalanche.ca/weather.
Avalanche Summary
Natural loose dry avalanches from size 1.5 to 2 were reported from alpine features facing North, Northeast, East and and Southeast over the weekend.
Snowpack Summary
The snowpack is extremely variable at this time, with wind scoured North facing slopes at treeline and above. South facing slopes have wind slabs at tree line and above, and may be hiding surface hoar from the previous spell of cold clear weather. Surface facetting has been observed in the region as a result of the recent cold weather and clear skies, and surface hoar up to 20mm has been reported in sheltered locations below 1900m. There are a number of surface hoar layers now buried in the snowpack that at present have been unreactive, with the most recent buried on Nov 24th. In shallow snowpack areas especially on northern aspects, there are reports of weak facetted layer at the base of the snowpack. With the recent warm temperatures, expect sun crust on solar aspects above 1500 metres.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.