Selkirk Mountains

Most slopes are generally safe from avalanches. You might be able to trigger an avalanche on upper-elevation slopes that face west through north to southeast where winds layered recent snow over older snow layers. You can find these problematic spots below ridgelines and in gullies that look filled-in, rounded, or pillow-shaped.

The steady onslaught of storms during November has transitioned to a period of quieter weather to start December across our forecast zones. This has helped the snowpack settle and find equilibrium, but not prevented snowpack change. Despite lower elevations being socked in below the stratus-fog layer, the mountains have seen plenty of sunshine since last weekend. These weather conditions have contributed to large diurnal temperature swings and lots of surface faceting. Field observations report various flavors of faceting ranging from large Surface Hoar grains to a pile of near-surface facets on wind-sheltered and shady aspects, and newly formed faceted sun crusts on southerly-facing slopes.

Weakening or softening of the upper snowpack has made it more difficult for a rider or machine to trigger an avalanche that breaks in older snow layers. This downward trend has been supported by multiple field observations throughout our forecast zones. Snowpack tests are requiring harder force to initiate a failure in these collapsible snow layers, and the overlying slab has become soft enough to help limit propagating failures in Extended Column Tests. While these conditions have allowed for us to venture into steeper and bigger terrain during the early season, this scenario is likely to spell trouble once we start stacking fresh slabs of snow on top of a weakening upper snowpack.

Digging deeper, the lower snowpack benefited from mild temperatures and bountiful snowfall during the first couple of storms in November. More or less steady snowfall limited the opportunity for the snow surface to facet and therefore, the bottom of our snowpack currently lacks widespread, discernable weak snow layers for most areas – the caveat are in places where overall snow depths are still less than 3 feet deep. Additionally, November storms arrived with lots of warm, moist air and fluctuating rain levels. This contributed to different snowpack layering between lower, mid, and upper elevations.

Multiple rain crusts lurk throughout the snowpack and rainfall on November 23 climbed above 7,000 feet. Recently, field observations have noted small, faceted grains starting to form around the November 23 crusts – primarily at elevations around 6,500 feet and higher. The fact this upper crust is close to the surface and directly affected by steep temperature gradients, we should anticipate these facets will not get stronger but only further weaken. These lingering persistent grains will likely come back into play once the next stormy period adds more load and stress. Additional load on top of weak persistent grains can increase the odds of a shallow avalanche breaking deeper and producing a larger, more dangerous avalanches.

Despite generally stable conditions at present, travel through the mountains with an investigative mindset. You can use small non-consequential test slopes to look for signs of instability before choosing to step into bigger, steeper terrain. Observing how weak the snow surface is on different aspects and elevations now will help you avoid an avalanche encounter once the snow train rolls back into the station.