Blue skies and a tricky surface slab; it is not the time to hit the big lines right now! Skiers on Bruins Ridge avoided a death fall in an avalanche they triggered yesterday by grabbing trees and holding on for their lives.
Weather Forecast
A mix of sun and cloud today, with an alpine high of -13*C and light W winds. Tuesday, a slight warming with alpine highs of -6*C and light W ridge-top winds. The next storm arrives Wed, with 15-20cm of snow, moderate SW winds, and freezing levels rising to 900m. Thurs could see up to 30cm, with strong SW winds and freezing levels rising to 1300m.
Snowpack Summary
The storm started dry and light, but finished warm and heavy, producing a very touchy storm slab. Temperatures have cooled dramatically overnight, but this new slab may take more time to bond to the old snow surface. The Dec 9 and Nov 21 interfaces are down ~120-140cm, are producing hard/sudden test results, and can be triggered in shallow areas.
Avalanche Summary
A skier triggered sz 2.5 avalanche from Bruins Ridge nearly swept 2 skiers over cliffs into 8812 Bowl. Field teams were able to ski cut sz 0.5 surface slabs on small, unsupported features. A natural avalanche cycle continued yesterday morning with numerous avalanches to size 3 through the highway corridor. Natural activity died down in the evening.
Confidence
Due to the number of field observations
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.