Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
Glacier.
Lots of light snow, combined with lots of wind, will cause new slabs to develop. Combine those hazards with the Christmas ski crowd and managing risk and exposure can be challenging. Remember that people might be above, or below you!
Weather Forecast
Today should be mostly cloudy with flurries bringing up to another 5-10cm. This will add to the ~30cm available for moderate to strong SW winds to transport and load lees. On Thursday, the next storm arrives dumping another ~20cm with gusty SW winds. By Friday the storm will start to taper off, with more flurries and gusty winds.
Snowpack Summary
Another 30cm of snow overnight, combined with strong SW winds, is building a new storm slab. It overlies surface hoar that was observed well into the alpine. Last weeks storm snow is settling into a stiffer slab, and the facetted Dec.18 layer is now down ~1m. Natural and skier triggered slabs on this layer have been observed recently.
Avalanche Summary
Yesterday skiers reported triggerable windslabs on a SW aspect at 2100m on McGill, and there were several size 2 and a size 3 natural avalanche from steep paths east of Rogers Pass. On Monday, a size 2 skier-triggered avalanche from steep, shallow, unsupported terrain carried a person over a large cliff and resulted in a rescue.
Confidence
Intensity of incoming weather systems is uncertain
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 Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.