We are in the midst of a natural avalanche cycle with copious amounts of rain below 2000m with more on the way. Avoid backcountry travel in avalanche terrain until the temperatures cool and precipitation stops.
Weather Forecast
The year of the pineapple express continues to deliver mild temperatures and heavy precipitation in the form of rain to 2000m with associated strong to extreme southwest winds at 3000m. This storm will persist into tomorrow afternoon before another wave hits. Freezing levels will drop by tomorrow with freezing levels to be around 1500m.
Snowpack Summary
The Jan 30 surface hoar/crust layer, which exists up to 2200m, is down 30-70cm, depth will depend on elevation The upper snowpack will be moist or wet to above 2000m. Jan 15 surface hoar layer is down 70-110cm and tests indicate it is still reactive in some areas.
Avalanche Summary
Natural avalanche cycle and avalanche control in progress along the highway corridor producing avalanches to size 3.5. Avalanches begin dry and end as moist onto their fans. On Tuesday skiers accidentally triggered a size 2.5 avalanche from a SE aspect at 2120m. The avalanche propagated ~200m wide and ran ~600m.
Confidence
Due to the number of field observations on Friday
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.