Navigate around wind loaded slopes and keep in mind the potential for surprisingly large avalanches due to isolated weak layers.
Strong southwest wind and a series of moderate snowfalls over the past few days has likely left reactive slabs in steep leeward terrain.
The snowpack across the region has some isolated areas where persistent weak layers linger, including surface hoar and/or facets above a crust 50 to 100 cm below the surface. This is a difficult problem to manage because it does not seem to exist in most terrain, but in the isolated places where it does exist it can produce large destructive avalanches.
Clearing weather after a front crosses the region on Wednesday night.
WEDNESDAY NIGHT: 5-15 cm of snow, moderate southwest wind, treeline temperature around -2 C.
THURSDAY: Cloudy in the morning then clearing in the afternoon, light north wind, treeline temperatures around -5 C.
FRIDAY: Mostly sunny skies, light wind, temperatures around -5 C.
SATURDAY: Mix of sun and cloud, light west wind, temperatures around -7 C.
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.
On Sunday there was 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, and illustrates how the current persistent slab problem is lingering in isolated areas.
Moderate snowfalls and strong southwest wind over the past few days has likely left hard surfaces and wind slabs in exposed terrain. Roughly 30-50 cm of recent snow is settling above a crust that extends up to 1900 m. The main feature we are monitoring in the snowpack is a layer of feathery surface hoar and/or faceted grains over a hard melt-freeze crust found 50 to 100 cm deep. Reports suggest this layer is strong and bonded in most terrain, but remains suspect in the isolated areas where it is preserved. Unfortunately we do not have a clear picture of where this isolated areas exist.
