Triggering avalanches may be possible in specific areas with stiff, wind-drifted snow or with a buried weak layer. Monitor for these conditions where you travel on Friday.
Strong winds have redistributed recent snow into hard wind slabs on lee features at upper elevations that may be possible trigger. Cornices are adjusting to a rapid load and may trigger avalanches on the slopes below.
A weak layer of surface hoar buried Jan 11 may be found 50-70 cm deep on open, sheltered slopes near and below treeline. There is uncertainty as to the distribution and reactivity of this persistent slab problem across the region.
Thursday night: Mostly clear, light northwest winds, alpine temperatures dropping to -20 C.
Friday: Mostly sunny, light northwest winds, alpine high temperatures near -14 C.
Saturday: Increasing cloud, light variable winds, alpine high temperatures near -16 C.
Sunday: Mix of sun and cloud, isolated flurries with a trace of accumulation, light variable winds, alpine high temperatures near -12 C.
Recent strong west winds have formed wind slabs in lee features at upper elevations that may be possible to human trigger. Over the last few days, operators in neighboring Glacier National Park reported several large (size 2-2.5) wind slabs releasing naturally on a variety of aspects (north, east, and south). Two natural cornice failures were reported in Glacier National Park on Wednesday releasing above north-facing slopes.
This MIN from Clemina Creek over the weekend reports that the Jan 11th surface hoar was cracking and propagating in sheltered treeline and below treeline areas where it was buried 40-50 cm deep.
Since field observations in this region are limited, please consider submitting your observations to the Mountain Information Network.
Recent winds have scoured snow surfaces, loaded cornices, and formed stiff wind slabs in alpine and upper treeline areas. These wind slabs sit over a variety of surfaces, including isolated surface hoar, sun crusts, and settling storm snow. A new sun crust may be forming on steep solar aspects, and there here have been reports of surface hoar growing on the snow surface.
50-70 cm of snow from the past week has buried a weak of layer of surface hoar that has shown reactivity in the north of the region. A MIN from Canoe Mountain on Tuesday reported a sudden pop or drop on this layer in snowpack test results. Observations are limited, so the distribution and sensitivity of this layer is uncertain and warrant careful assessment. Below 1600 m, 20-30 cm of snow is settling above a decomposing melt freeze crust.
Deeper in the snowpack, a couple of older persistent weak layers may still be identifiable from late and early December, consisting of surface hoar and a crust with faceted snow and buried anywhere from 100-200 cm deep. Prolonged periods of inactivity and unreactive snowpack test results suggest that these layers have trended towards dormancy.
