Heads up for a significant storm this weekend. New snow and high winds will elevate the avalanche danger.
Confidence
Fair - Forecast snowfall amounts are uncertain
Weather Forecast
Saturday: The westerly flow becomes stronger bringing light to moderate amounts of precipitation. Moderate westerly winds at ridge top and freezing levels hovering around 1200m. Mostly cloudy conditions throughout the interior.Sunday: The arctic front rapidly moves southward colliding with a low pressure system moving eastward across the province. Moderate to locally heavy amounts of precipitation over the Columbia Mountains with the western ranges likely getting hit the hardest. Winds will be moderate to strong westerly and freezing levels descending to valley bottom.Outlook for Monday: Clearing skies and cold temperatures as the arctic front embeds itself into Southern British Columbia. Strong northerly winds as outflow conditions prevail.
Avalanche Summary
No recent avalanches have been reported. However, new snow and strong winds over the weekend will likely cause a spike in natural avalanche activity.
Snowpack Summary
Snow depths are approximately a metre at treeline elevations but depths vary across the region. According to snow pillow data, the snowpack is seasonably below average. Recent storm snow has buried a variety old snow surfaces including a melt freeze crust on south facing slopes and surface hoar. The recently buried surface hoar is likely most prevalent on shady, sheltered slopes at upper treeline and lower alpine elevations. The upper and mid snowpack is generally well settled and overlies a layer of surface hoar (50-90cm). This layer appears to be spotty and drainage specific in distribution. Digging deeper, an October melt-freeze/rain crusts can be found near the base of the snowpack. These deeper layers may have become more difficult to trigger. However, the weight of new snow that is forecast for the weekend could be the tipping point for these layers, producing large and destructive avalanches.
Problems
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.
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.