Conditions will change rapidly as we enter the weekend. Watch for sluffing from steep terrain at all elevations and for signs of early wind slab development in the alpine.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
The first wave of precipitation is expected to reach the interior late Thursday night or early Friday morning. 10-20cm of new snow is expected in the south of the region for Friday. Freezing levels are expected to be 1200-1500m and alpine winds moderate from the SW. A weak ridge will keep Friday night and Saturday morning mainly dry before the next storm front arrives on Saturday afternoon or evening. Freezing levels on Saturday will rise to around 1500m or so and alpine winds will increase to strong from the SW. Saturday night and Sunday should yield another 20-40cm of snowfall up high. Freezing levels on Sunday may rise as high as 2000m and winds will remain strong.
Avalanche Summary
No new avalanches have been reported since last weekend. On Sunday, snowmobiles remotely triggered a persistent slab with a crown depth around 1.5m in the Allan Creek area. On Saturday, two size 2 remotely triggered persistent slab avalanches were reported. These were triggered from 250m away and released 80-100cm down on the old rain crust from early November. These occurred around 2000-2200m elevation on NW aspects.
Snowpack Summary
The new snow sits on a layer of large surface hoar. Up to around 1800m elevation this surface hoar sits on a hard rain crust. Above 1800m the surface hoar sits on well settled and faceted snow. The early November crust/facet layer is down around 1 m in the south of the region, probably less in the north.
Problems
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
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.