Natural avalanches possible, human triggered probable.
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 possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
North Columbia.
A Special Public Avalanche Warning is in effect. Copy this link to view details: http://bit.ly/2nSOUyX
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Tuesday
Weather Forecast
MONDAY: Mainly sunny, with increasing clouds late in the day. Light winds. Treeline temperature near -10.TUESDAY: 10-15 cm snow. Moderate westerly winds. Treeline temperature near -5.WEDNESDAY: Flurries. Light winds. Treeline temperature near -8.More details can be found in the Mountain Weather Forecast.
Avalanche Summary
A very large, widespread avalanche cycle was observed on Thursday, with a few events continuing on Friday. Slopes of all aspects and elevations ran full path and reached valley floor. In some cases, mature timber was smashed. These failed on all of the persistent weak layers discussed in the snowpack section. Avalanches involving only the recent storm snow were also very large. Explosives continued to produce very large persistent slabs on Saturday.The natural cycle has wound down, but human-triggering remains a real concern. Avalanches are most likely to be triggered with a large load (like a snowmobile landing a jump, a cornice fall, or a solar-triggered avalanche stepping down), or from a thin-spot trigger point, like around trees or rocks. You might be surprised by how large an avalanche can be triggered and how far it could run.
Snowpack Summary
Strong north to north-westerly winds have shifted 25-70 cm recent storm snow into wind slabs on lee slopes. This adds to an existing storm slab that's 1-2.5 m deep from the last couple of weeks' accumulation. Several persistent weak layers make up a troublesome snowpack. In the top 1.5-2.5 m of the snowpack, two surface hoar layers buried in January can be found. Expect to find one or other of these on all aspects and elevations.Deeper in the snowpack (around 200 cm deep) is a facet/crust/surface hoar layer from December, most prevalent at and below treeline.Near the base of the snowpack is a crust/facet combo, most likely to be triggered from thin spots in the alpine.All of these layers have produced large avalanches recently. The wide distribution and ongoing reactivity of these layers suggests that avoidance through choosing simple terrain is the best strategy.
Problems
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.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.