The Winter Permit System is in full effect. There will be Active Avalanche Control today in the Highway Corridor.
Weather Forecast
Rain and wet flurries today, as the atmospheric river or pineapple slowly departs Rogers Pass. Freezing levels will lower, winds will slowly decrease and precipitation will gradually subside. However currently we have a moderate rain fall, extreme winds and high freezing levels!
Snowpack Summary
150cm of new snow fell in the last seven days at tree line, followed by 40mm of rain. This combination has weakened the snowpack significantly. Below tree line the snowpack has become isothermal. At higher elevations storm and wind slabs have developed, and the upper snowpack layers are being saturated by the rain and warm temperatures.
Avalanche Summary
A large and destructive avalanche cycle started yesterday. The peak of this cycle will be this morning, with approximately 30-40mm of rain in the start zones over the last 24 hours. We've observed lots of loose wet avalanches in the highway corridor and slab avalanches. This is the largest and most significant cycle we've seen so far this winter.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.