Purcells

A Special Public Avalanche Warning (SPAW) is in effect for this region. Natural avalanche activity will taper off somewhat on Saturday, but THE POTENTIAL FOR HUMAN TRIGGERED AVALANCHES REMAINS LIKELY.

Moderate - Timing, track, or intensity of incoming weather system is uncertain

FRIDAY NIGHT - Cloudy with flurries, 5-10 cm / southwest winds , 25-70 km/h / alpine low temperature near -10SATURDAY - Cloudy with sunny periods and isolated flurries / south to southwest winds, 20-30 km/h, gusting to 55 km/h / alpine high temperature near -8SUNDAY - Cloudy with sunny periods and isolated flurries, up to 5 cm / south to southwest winds, 20-35 km/h / freezing level 1400m / alpine high temperature near -2, low temperature near -7MONDAY - Mainly cloudy with flurries, 5-15 cm / southwest winds, 20-60 km/h / freezing level 1500m / alpine high temperature near -3, low temperature near -7

Avalanche activity continues in the Purcells. Numerous human and explosives avalanches up to size 2.5 were reported on Thursday and Friday. Several of these were triggered from a distance (remote triggered). A natural avalanche cycle to size 4 was also reported in the region on Friday.In the neighboring Glacier National Park region, artillery avalanche control resulted in numerous avalanches between size 2-3.5 on Thursday and Friday. Many of the larger avalanches were nearly reaching the bottom of their run out zones. Reports suggest that some of these avalanches may have stepped down to the weak layer buried in mid November.

60-100 cm of new snow sits on a weak layer of facets (sugary snow), surface hoar (feathery crystals), and a sun crust (on south facing slopes). Strong winds have promoted widespread slab formation.Another layer of surface hoar and sun crust is now buried 100-150 cm. The potential may exist for smaller avalanches to step down to this deeper layer, resulting in large avalanches. The most likely areas for this layer to be a problem is where the surface hoar sits on the sun crust, which is most likely on steep south facing terrain at treeline.At the base of the snowpack is a crust that formed in late October. This layer is likely only a problem on large, steep alpine features with a shallow snowpack. It likely take a large trigger, such as a cornice fall, to produce an avalanche on this layer.