Triggering large deep persistent slab avalanches remains a concern on steep rocky slopes at higher elevations, especially ones getting hit by the sun.
Weak snow at the bottom of the snowpack continues to pose a deep persistent slab avalanche problem. The most recent activity has been focused around the Golden area, but steep rocky terrain throughout the region should be treated with caution. Use extra caution on and below big alpine slopes getting hit by the sun.
TUESDAY NIGHT: Clear, light north wind, alpine temperatures drop to -18 C.
WEDNESDAY: Sunny, light north wind, alpine high temperatures around -6 C.
THURSDAY: Sunny, light southwest wind, alpine high temperatures around -6 C.
FRIDAY: Sunny, light southwest wind, alpine high temperatures around -6 C.
Reports over the long weekend were primarily limited to a few small (size 1) wind slab avalanches, dry loose avalanches, and cornice falls.
There have also been a few sporadic large avalanches over the past week. Most recently, a large (size 3) deep persistent slab avalanche was remotely triggered on Sunday just outside the forecast region near Mt. Seven. Photos in the Mountain Information Network report show this avalanche was initiated by a skier causing on whumpf on a ridge that triggered a smaller wind slab on an east-facing alpine slope that stepped down to the basal facets. Another size 2.5 deep persistent slab avalanche was observed in steep rocky alpine terrain on a southwest slope near Golden on Thursday (see MIN report) and a large snowmobile triggered avalanche was reported on a convex roll at treeline at Quartz Creek on Wednesday (see MIN report). These isolated large avalanches highlight the importance of careful snowpack and terrain evaluation in the Purcells.
Sunny weather could weaken cornices and the upper snowpack on steep south-facing slopes. Surface conditions are a mix of low density snow in sheltered terrain, sun crusts on south-facing slopes, and isolated wind slabs at higher elevations. At lower elevations (below 1600-2000 m) 20-40 cm of snow sits above a hard rain crust. The middle of the snowpack is strong, but the base of the snowpack contains basal facets that have resulted in sporadic large deep persistent slab avalanches, especially in shallow rocky start zones.
