A large natural avalanche cycle is occurring and the storm is just beginning. Avoid all avalanche terrain.
Weather Forecast
The "pineapple express" is just hitting us. Lots of precipitation, mild temps and high alpine winds are forecast over the weekend. Up to 40cm are expected over the next 24hrs. Freezing levels may rise to 1600m, and southerly winds in the alpine may reach 125km/hr today. The intense loading will rapidly cause danger to rise.
Snowpack Summary
Nearly 30cm of heavy, and moist at lower elevations, snow has fallen in the last 12 hours. This has rapidly loaded the Feb 12 surface hoar and crust layers which are now down 80 to 90cm. This layer is most prevalent at and below treeline. In the alpine, southerly winds are transporting snow rapidly loading slopes and forming new windslabs.
Avalanche Summary
A natural avalanche cycle is just beginning as the storm hits. Rapid loading by snow and moderate S'ly winds are triggering avalanches. Large natural avalanches to size 3 have been observed along the highway running to valley bottom. Precip rates and wind speeds will increase today; expect natural avalanches to run full path in the backcountry.
Problems
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.
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.