Don't underestimate the avalanche danger at this time. Forecast new snow and rain could overload a significant weak layer with the potential to release very large avalanches. See this blog post for additional info: http://bit.ly/1HHQrK2
Confidence
Fair - Intensity of incoming weather systems is uncertain
Weather Forecast
A series of wet storms are set to impact the coast until Tuesday morning then a cooling trend. Saturday night: 15-25 mm precip can be expected between 4pm Saturday and 4am Sunday with freezing levels around 1700 m and strong southwesterly winds. Sunday: A further 15-25 mm precip is expected with freezing levels around 1900 m and southwest ridgetop winds gusting to 60 km/h. Monday: Another pulse looks to bring 10-20 mm precip with freezing levels around 1900 m and southwest ridgetop winds gusting to 60 km/h. Tuesday: Possibility of lingering storms that could bring highly variable precipitation. A cooling trend is expected to lower freezing levels to around 1000 m. Winds are expected to diminish.
Avalanche Summary
Over the past week, very large slab avalanches have been running on the mid-March persistent weak layer. What makes this spooky is that the majority of these avalanches have been remote triggered, some from as far as 200m away. This interface remains very reactive. While it's a few days old now, the photo in this Mountain Information Network post provides a very powerful visual: https://bit.ly/1CS2Nld
Snowpack Summary
This region has a very serious persistent slab problem that exists under the upper layers of dense storm snow. Depending on how much recent snow has fallen, a facet/crust persistent weak layer buried mid-March lies anywhere from 50-150 cm below the surface. This interface has been incredibly volatile recently and remains sensitive to human triggering, especially where the slab is thinner. Recent compression tests have produced sudden planar failures at this interface. At lower elevations, rain has saturated the snowpack. Layers below the critical mid-March interface are generally considered to be well-settled and strong.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.