Don't let sunny skies and good snow lure you into complex terrain. Recent avalanches have been large. Avalanche danger may be improving as the likelihood of triggering them diminishes, but if you're unlucky enough to do so, consequences can be high.
Recent snow and moderate wind have created deep pockets of reactive wind slab in lee terrain features at upper elevations. These will likely remain sensitive to human triggers.
A weak layer of surface hoar that was buried around Christmas is now down about 50-80 cm and is most prevalent at treeline and below treeline.
Two more persistent weak layers buried in early/mid-December are now 90-150 cm below the surface. The form and distribution of these layers are highly variable and may vary significantly from one valley to the next, and between elevation bands.
Friday night Mostly cloudy, light west wind, freezing level valley bottom.
Saturday A mix of sun and cloud / light southeast wind, alpine high -7, freezing level valley bottom.
Sunday: Mostly cloudy, light southeast wind, alpine high -6, freezing level 600 m.
Monday: Flurries, trace, light to moderate south wind, alpine high -6, freezing level 900 m.
We have received few reports of avalanche activity in the region since the mid-week storm slab avalanche cycle produced natural avalanches size 2-3.5. But with similar snowpack structure and recent weather patterns to neighboring Glacier National Park and South Columbia regions, we suspect that recent avalanche activity has been similar, but has gone unreported due to less backcountry traffic.
Natural storm slab avalanches size 1.5-2.5 have been reported in GNP as recently as Friday. Notable avalanches in South Columbia include several skier triggered incidents around size 2 in the RMR slackcountry and a few natural persistent slab avalanches size 2.5-3 on northerly aspects in the alpine running on the early December persistent weak layer. See South Columbia avalanche summary for details.
Around 50-80 cm of recent snow sits on a weak layer of surface hoar that was buried around Christmas. This layer is most prevalent at and below treeline. Previous moderate to strong winds have redistributed surface snow, creating wind slabs at wind exposed elevations.
A couple of persistent weak layers buried in early/mid-December are down about 90-150 cm. Generally, they can be found as a layer of surface hoar above in close proximity to a crust/surface hoar layer. The form and distribution of these layers are highly variable and conditions may differ significantly from one valley to the next.
