Wind slab avalanches remain likely at higher elevations, plus concerns about a buried weak layer warrants careful terrain choices.
Strong wind over the weekend formed unstable wind slabs at upper elevations, especially along ridges. Fresh wind slabs are expected to form on Wednesday.
It remains possible to trigger a weak surface hoar layer buried about 100 cm below the surface. Convex rolls at treeline and below treeline elevations are the most likely places to trigger this layer. Recent reports suggest this problem is more prevalent in southern parts of the region.
MONDAY NIGHT: Clear skies with a few clouds, light to moderate wind from the west, alpine temperatures drop to -18 C.
TUESDAY: Mix of sun and cloud in the morning with increasing clouds and isolated flurries in the afternoon, light wind in the morning then moderate gusts from the southeast in the afternoon, alpine high temperatures around -12 C.
WEDNESDAY: 5-15 cm of new snow overnight then a mix of sun and cloud in the afternoon, light wind from the north, alpine high temperatures around -15 C.
THURSDAY: Mix of sun and cloud with some light flurries of snow, light wind from the west, alpine high temperatures around -15 C.
Windy conditions over the weekend resulted in natural avalanche activity at higher elevations (such as these MIN reports from Hasler and Bijoux). Most of the natural wind slab avalanches were reported on north and east facing terrain. Several large persistent slab avalanches were reported on buried surface hoar last week, but there are no reports of avalanches on this layer over the weekend. As this layer gets buried deeper it becomes less likely to trigger, but the consequences are high.
A series of big storms last week ended with strong wind that heavily affected open terrain and formed unstable wind slabs in steep lee terrain. Storm totals range from 40-80 cm, meaning deep powder can still be found in sheltered terrain. The main layer of concern is a feathery surface hoar layer that was buried around Christmas and is now resting about 100 cm below the surface. While this layer was very reactive across the region last week, recent reports suggest that it is now a much more spatially variable problem. There has been more recent evidence of this problem in the southern parts of the region around McBride and the McGregors, but preserved surface hoar could potentially be found on sheltered convex slopes anywhere across the region.
