Sporadic large natural persistent slab avalanches have recently been reported in this region. This low likelihood, high consequence scenario is best avoided by choosing conservative terrain away from overhead hazard.
Lingering wind slabs remain possible to human trigger in isolated areas. 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.
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.
FRIDAY NIGHT: Partly cloudy / Light, southwest ridgetop wind / alpine low temperature -16 / Freezing level valley bottom.
SATURDAY: Mix of sun and cloud / Light, southwest ridgetop wind / alpine high temperature -8 / Freezing level valley bottom.
SUNDAY: Cloudy / Moderate, west ridgetop wind / alpine high temperature -7 / Freezing level valley bottom.
MONDAY: Cloudy / Strong, west ridgetop wind / alpine high temperature -5 / Freezing level 1200 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 report HERE.
Several size 1.5 human triggered avalanches were reported on Wednesday in the top 30 cm of storm snow. Over the past few days there have been several natural and explosive triggered storm slab avalanches in the size 1.5-2.5 range, as moderate amounts of snow and wind each day have kept the avalanche danger elevated.
Last Sunday there was a remotely triggered persistent slab avalanche in a north facing gully at 1350 m (see the photo here). The avalanche failed on a 50 cm deep surface hoar layer. This layer has been reported in sheltered terrain below treeline.
