The parade of storms has woken up a nasty persistent slab and more snow is coming. The consequences of triggering an avalanche could be much higher than surface instabilities suggest.
Weak layers that formed during the January drought have become active with increased load and warm temperatures. Smaller storm slabs may step down to these layers and become large avalanches.
New snow and high winds should form a new storm slab problem to manage on Monday. Expect hazard increasing with elevation and greatest in leeward terrain. Storm slabs at higher elevations have potential to step down to deeper layers.
Periods of sunshine, where they emerge, will destabilize new snow on sun-exposed slopes. Loose avalanches may run naturally or with a human trigger.
An increasing number of natural and controlled avalanches have been reported since the parade of storms began. Wind slabs and storm slabs to size 2 were not unexpected, however Saturday saw a marked increase in avalanches failing on or stepping down to the late-Jan/early Feb persistent layers around 60 cm deep (and counting) in the snowpack. This problem remains a serious concern as the next storm takes aim at the coast Sunday night.
15 - 25 cm of new snow should accumulate overnight Sunday, bringing storm totals to ~50 - 80 cm, all of it affected by strong southerly winds. These storm totals overlie problematic faceted snow, or surface hoar in sheltered terrain. In exposed terrain, sun crust (an excellent bed surface for avalanches) or previously wind-affected snow are more likely.
A weak layer that was buried at the end of January is now 60 to 100 cm deep in the snowpack. This may present as a crust on sunny slopes, sugary facets in most places, and surface hoar in sheltered spots. Saturday's storm woke this layer up decisively and both natural avalanches and human triggering on this layer are a serious concern.
The snowpack below is strong.
Sunday Night
Cloudy with snow showers bringing 15 - 25 cm of new snow, increasing with elevation, rain below about 1000 m. 30 to 50 km/h southwest ridgetop wind. Freezing level 1300 m.
Monday
Clearing over the day, clouding over in the afternoon. 20 to 50 km/h southeast ridgetop wind. Freezing level 1200 m - 1500 m.
Tuesday
A mix of sun and cloud after about 5 cm accumulation overnight. 5 - 15 km/h variable ridgetop wind. Freezing level 1200 m - 1600 m.
Wednesday
Becoming sunny. 30 - 50 km/h southeast ridgetop wind. Freezing level shooting to 2400 m.
More details can be found in the Mountain Weather Forecast.
