A dusting of flurries and increasing winds may build fresh wind slabs by the end of the day.
Up to 10 cm is forecasted around the region. Where winds reach upward of 20 km/h, fresh windslabs may form in lee features.
Wind slabs have been most reactive recently below corniced ridges or on alpine-looking slopes at tree line where wind slabs developed over preserved surface hoar. Cornices are large - give them space.
A weak layer of surface hoar buried Jan 11, and about 25-50 cm deep may be possible to trigger on open, sheltered slopes near and below treeline (above 1700 m). Recent activity on this layer has been specific to the southern half of the region.
Tuesday night: Mostly cloudy / southeast winds, 15-25 km/h / alpine low temperature -5
Wednesday: Cloudy with isolated flurries, 5-10 cm / southeast winds, 15-25 km/h / alpine high temperature -12
Thursday: Cloudy with scattered flurries, 5-10 cm / southeast winds, 10-15 km/h / alpine high temperature -9
Friday: Cloudy with sunny breaks / south winds, 10 km/h / alpine high temperature -8
On Sunday in Glacier National Park, a skier triggered a size 2 avalanche upon entrance into a cross-loaded terrain feature.
On Saturday, a skier triggered a size 2 wind slab avalanche of a layer of surface hoar; the crown averaged 25 cm. The avalanche was triggered just below an open and corniced ridge feature at tree line, and occurred in the southern end of the forecast region in the Selkirks. As you step out into steeper terrain, a slope-specific assessment is recommended
Other recent avalanche activity includes small size 1-1.5 wind slabs, a few large cornice failures, and loose dry sluffing in steep and southerly terrain.
We're continuing to track a layer of surface hoar from early January, the most recent activity reported on this layer was January 18, when several operators in the region reported small (size 1-1.5) human-triggered avalanches releasing on a weak layer of surface hoar on north, east and southeast aspects at treeline and below treeline elevations. These avalanches were breaking 25-45 cm deep.
A dusting of low density snow overlies a widespread layer of surface hoar up to 10 mm in sheltered areas around treeline. The snowpack boasts a variety of surfaces including scoured and pressed surfaces in exposed terrain, large cornices, isolated wind slabs, and variable wind affected and facetted snow in more sheltered terrain. Cold temperatures are encouraging surface faceting and breaking down wind slabs. A thin sun crust may be found on steep solar aspects. Below 1700-1800 m, 20-30 cm of snow is settling above a decomposing melt freeze crust.
Observers continue to find a preserved layer of surface hoar down 25-50 cm in sheltered, open slopes at and below treeline. Most recent reactivity has been reported in the Selkirks towards the south of the forecast region (see avalanche summary). On the other hand, snowpack tests on this layer are trending to hard and resistant shears, as such it continues to warrant slope-specific assessment.
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.
