Avalanche Forecast

Fair - Timing, track, or intensity of incoming weather system is uncertain

Thursday: Mainly cloudy with light snow flurries. Freezing level near valley bottoms with light variable alpine wind. Friday: Cloudy with sunny periods and isolated light snow flurries. Freezing level reaching 1500 m with light southerly alpine wind. Saturday: Mainly cloudy with light snow bringing 5-10 cm of accumulation. Freezing level around 1200 m and light SE alpine wind.

Reports from Tuesday include isolated small human triggered wind slab avalanches and dry loose sluffs on northerly aspects, and snowballing, pinwheeling, and sluffing on sun-exposed slopes. Recent very large deep persistent slab avalanches in neighboring regions highlight a low probability, but high consequence avalanche problem that also plagues the South Columbia region. These highly destructive and largely unpredictable avalanches are expected to be isolated, but certainly possible anywhere at anytime.

Warm temperatures and blasts of solar radiation are moistening the surface snow. Weaknesses exist within and under the 40-70 cm of rapidly settling recent storm snow, including small surface hoar, thin sun crusts, rain crusts, and/or small facets. These weaknesses are currently reactive to light triggers, especially on wind-loaded slopes. Some big cornices have also become weak.There are three persistent weak layers that contribute to a highly variable, fundamentally unstable, complex snowpack with step-down potential. The mid-March sun crust/surface hoar layer down 50-80cm still has potential for human-triggering in isolated areas. The early-March crust/facet/surface hoar layer down around 80-120cm has become less susceptible to human-triggers, but still has the potential to produce large avalanches, and we continue to see fractures stepping down to this layer. The mid-February crust/facet/surface hoar layer is typically down at least 1.5m and direct triggering has become unlikely. However, large loads like cornices or smaller avalanches stepping down can still trigger this layer and produce very large avalanches.