Wind slabs are expected to remain reactive to human-triggering. Avoid wind-loaded areas and watch signs of instability.
Choose conservative, low consequence lines. Riders have been surprised in recent days by large avalanches failing on a weak layer of surface hoar.
30-50 cm of recent snow and moderate southwest winds formed fresh wind slabs in lee areas in the alpine and treeline. These slabs may be surprisingly deep and propagate widely where they are sitting on a weak layer of surface hoar or a sun crust.
The most recent storm buried a weak layer of surface hoar. This layer has produced large and surprising human-triggered avalanches in the past few days and reactivity is expected to persist into the week.
The most reactivity on this layer has been seen on wind-loaded, east-facing slopes in the alpine and treeline, but caution should be taken on all aspects as this problem unfolds.
A series of frontal systems coming in off the coast will bring light precipitation throughout the week.
Tuesday Overnight: Mainly cloudy, light precipitation. Localized areas up to 10 cm accumulation. Moderate to strong westerly winds. Freezing level dropping to 900 m.
Wednesday: Partially cloudy, light precipitation. Localized areas up to 10 cm accumulation. Moderate to strong westerly winds. Freezing level rising to 1500 m.
Thursday: Mainly cloudy, light precipitation. Moderate to strong westerly winds. Freezing level 1500 m.
Friday: Partially cloudy, light precipitation. Moderate to strong southwesterly winds. Freezing level rising to 1500 m.
On Monday, several natural wind slabs were reported on easterly aspects at treeline as strong winds redistributed the new snow. A few natural wet loose avalanches occurred at treeline and below as a result of solar radiation and warm temperatures.
Numerous natural and sledder-triggered avalanches were reported throughout the weekend in the Pine Pass area down 25-70 cm, all failing on surface hoar. The most reactivity has occurred on wind-loaded, northeast aspects. Most notably, a size 2.5 sledder-triggered avalanche occurred near Bijoux Falls. The full report can be seen here.
A few sledder-triggered avalanches up to size 2 were reported in the Renshaw area on Sunday. These storm slabs were failing on a weak layer of surface hoar down 25-40 cm.
Continued light precipitation will add to 30-60 cm of recent settling storm snow. In the alpine and treeline, southwest winds have redistributed the new snow into wind slabs in lee areas. Below treeline, moist snow or a melt-freeze crust can be expected from rain and warm temperatures.
This new snow is sitting on various surfaces, including hard wind-affected snow, sun crusts on southerly slopes, and most notably large surface hoar on shady or sheltered slopes. This layer of surface hoar is expected to remain problematic in the coming days, with the most reactivity observed in the Pine Pass and Renshaw area.
The mid and lower snowpack is generally well-settled and strong in most areas, with multiple crusts throughout. No recent persistent slab avalanches have been reported on these layers.
