The current storm is ramping up avalanche danger where new snow is accumulating. Choose conservative terrain and watch for wind loaded features.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
SATURDAY: New snow amounts 5-10 cm accompanied by moderate westerly winds. Freezing levels to 1100 metres with alpine temperature to -6SUNDAY: Isolated flurries with moderate northwest winds shifting to northeast. Freezing levels dropping to valley bottom with alpine temperatures to -9.MONDAY: No new snow, light winds from the northeast, freezing levels dropping to valley bottom with alpine temperatures to -12.
Avalanche Summary
Fresh storm slabs are increasing the load on a weak layer that was until now too shallow to present a significant hazard. Expect both the reactivity and the destructive potential of this layer to increase as new snow accumulates and settles. Increased loading also raises concern for a deep persistent layer that is now buried up to 200cm deep in the snowpack. Both natural and rider triggerable loose dry avalanches out of steep terrain can also be expected as new snow accumulates.
Snowpack Summary
A fresh storm slab is blanketing the region, continuing to bury a surface hoar layer that could be found up to 15cm deep in the snowpack on Thursday. Areas with this layer and where previously wind affected surfaces exist will be more reactive as the new load increases. Watch for shallow wind affected areas that will not gain strength as quickly as deeper, well settled snowpack areas. Snow depths increased rapidly last week, bringing treeline snow depths to about 200 cm. The mid-November crust is buried anywhere from 20-200 cm depending on aspect and elevation. While this crust has been unreactive thus far, increasing load may bring it to its breaking point, especially in areas with shallow or variable snowpack depth.
Problems
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.