Avalanche Forecast

Good

Sunday: Moderate to heavy snow. Freezing level 500m, rising to 1000m by afternoon. Strong south-westerly winds.Monday: Moderate snow. Freezing level valley bottom. Light to moderate north-westerly winds.Tuesday: Light snow. Freezing level valley bottom. Light to moderate westerly winds.

As I write this, it's still too early for reports of storm-related avalanche activity, but I expect a natural cycle is well under way. Occurrences throughout the week illustrate the unpredictable nature of persistent weak layers in the upper snowpack. On Thursday, a skier triggered a size 2.5 slab very easily and very close to recent ski tracks, which failed on buried surface hoar. On Wednesday, a cornice fall triggered a size 2 slab on a north aspect, which failed on the Feb 16. weakness. On Tuesday, numerous size 2-3 avalanches ran naturally, or with a remote trigger, on a variety of slopes. Most failed on upper snowpack persistent weaknesses. These layers are touchy and are likely to fail under the new storm load, creating large or widely-propagating avalanches.

Snow is falling with strengthening winds and rising temperatures onto variable surfaces including surface hoar and facets. This is creating a nice recipe for new storm slab and wind slab instabilities. Persistent weak layers buried in February are a key concern at all elevations and could be triggered by storm slabs, wind slabs or sluffs, or with a light additional load (like you). Avalanches may be unexpectedly large, given the amount of fresh snow. Large cornices also loom as potential triggers for deep avalanches.