Selkirk Mountains

Incremental loading followed by cool stable weather has contributed to a generally stable and safe snowpack across the forecast zones. As snow and wind move into our region this afternoon the possibility of encountering new wind slabs increases. Places where persistent weak layers are closer to the surface, like steep rocky terrain and wind scoured slopes, are where encountering a persistent slab avalanche, although unlikely, may still be possible.  Continue to evaluate terrain and if you are unsure back off and choose slopes with lower angles and safe runouts. 

A recent D3 glide avalanche and observation of several glide cracks in the Silver Valley/Northern Bitterroot Zone warrant attention. Give glide cracks a wide clearance and do not travel below them as glide avalanches can be large and difficult to predict.

Today’s avalanche problems are similar to yesterday’s, with the caveat that avalanche hazards will increase with arrival of new snow and wind this afternoon. Variable winds with speeds that are sufficient enough to transport new and existing snow will create fresh wind slabs. Due to the changing wind direction, these denser slabs will extend their reach and build throughout the day. Broad openings have better odds at developing larger hazards quicker than more treed areas near the timberline where similar slabs may be more isolated. You can use small, test slopes to inspect sensitivity of fresh drifts before venturing out into steeper, bigger slopes or simply stick to wind-sheltered areas and lower elevation terrain.

With each passing day, deeper faceted grains continue to become less of a concern, but not totally in a state of dormancy just yet. The weight of the slab sitting above numerous faceted rain crust is likely helping compress these interfaces and take the bite out of them. The further these weaker interfaces sit below the surface, the less likely it is for a rider to impact them and trigger a slide. Maybe it takes a larger trigger like a snowmobile trenching through the slab or a large cornice caving off from above? Or maybe it requires finding the shallow spot on a slope to awaken the sleeping monsters?

During times of lower-likelihood, higher consequence we often rely on solid terrain management to help offset the realm of uncertainty. With less frequent field observations above 7,000 feet lately, know that venturing higher in elevation could push you into terrain where these faceted grains may be more preserved but the slab above will likely be thicker and stiffer. Avoid steep, rocky places where more trigger spots are abundant on a slope, and pick slopes free of vegetated runouts or terrain traps to account for the "what-if" scenario. Be mindful of other groups recreating around you and only expose one person to a slope at a time.

A recent large glide avalanche that occured on the night of Januarly 6th in the St. Regis Basin, visable from Lookout Pass ski area, and several glide cracks in the Silver Valley are worth noting. Glide avalanches can be composed of wet, moist, or almost entirely dry snow, and can release under warm regimes and cold regimes. They occur on very specific slopes where the ground surface is relatively smooth, such as slick bedrock or grassy slopes. Glide Avalanches are often preceded by full depth cracks (glide cracks) that are visible across the slope, though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, but natural failures are very challenging to predict. Because Glide Avalanches only occur on very specific slopes, safe travel relies on identifying and avoiding those slopes. Open glide cracks are a significant indicator, especially cracks that have opened recently, as are recent Glide Avalanches.