Strong westerly winds may form small reactive wind slabs throughout the day. Sporadic large natural persistent slab avalanches have recently been reported in this region.
Strong winds may form fresh wind slabs throughout the day on lee features at treeline and above. Wind slabs in motion may step-down to deeper weak layers resulting in large avalanches.
Wind slabs in motion and cornice falls have recently produced some very large avalanches failing on a crust down around 150 cm. Human triggering of this layer is most likely in steep, rocky slopes with a shallow or thin to thick snowpack.
SATURDAY NIGHT: Cloudy / Moderate, west ridgetop wind / alpine low temperature -12 / Freezing level valley bottom.
SUNDAY: Mostly cloudy with sunny periods / Strong, west ridgetop wind / alpine high temperature -7 / Freezing level valley bottom.
MONDAY: Cloudy with isolated flurries; 0-3 cm. / Strong, west ridgetop wind / alpine high temperature -6 / Freezing level 1200 m.
TUESDAY: Snow; 5-10 cm. / Extreme, southwest ridgetop wind / alpine high temperature -5 / Freezing level 1500 m.
A couple large (size three) naturally triggered persistent slab avalanches were reported on large alpine features on Thursday. These avalanches were triggered by either smaller wind slabs in motion or cornice falls. Another reminder of the "low probability; high consequence" scenario that persistent slab problems often create. See MIN reports HERE.
Lingering wind slabs formed by recent snow and wind remain possible to human trigger in isolated areas. Roughly 30-50 cm of recent snow is settling above a crust that extends up to 1900 m. In isolated areas below treeline, this recent snow may be sitting on a weak layer of surface hoar.
The main feature we are monitoring in the snowpack is a layer of weak facets(sugar snow) over a hard melt-freeze crust found around 100-150 cm down. Recent sporadic, large naturally triggered avalanches have occured on this layer on large alpine slopes and were triggered by either smaller wind slabs in motion or cornice falls.
