Purcells

We are dealing with a complex avalanche scenario. There is uncertainty in how buried weak layers will adjust to the warm temperatures. Conservative decision making is still recommended.

Freezing levels are forecast to remain high through Monday (up to 3000m) before gradually falling over Tuesday and returning to valley bottom by Wednesday. Winds will remain moderate from the south west with a possibility of showers and flurries on Tuesday.

We are moving into a complex avalanche scenario where touchy conditions are likely to persist. A snowpack with several critical avalanche layers has seen incremental loading in the form of new snow and more recently rain. Two recent avalanche cycles have produced increasingly large avalanches primarily on the mid-January surface hoar layer. While the region will see little to no precipitation through the coming forecast period, I anticipate that natural avalanches will remain possible and human triggered avalanche likely as the upper snowpack adjusts to the warm temperatures. Avalanche danger will be higher on slopes exposed to the sun. Warming temperatures will also make cornices more likely to collapse, which in turn could be sufficient to trigger a deep slab avalanche. I would be wary of overhead hazard. At lower elevations I suspect there is the potential for loose wet and wet slab avalanches.

Warm temperatures are encouraging the recent snowfall to rapidly settle into a soft slab. Moderate to strong southwest winds have created wind slabs in lee features. A weak layer of surface hoar buried mid-January lies between 35 and 50 cm below the surface. This layer has been responsible for the majority of the recent avalanche activity and I suspect that we will see it continue to produce avalanches as the snowpack adjusts to the recent snowfall and continued warm temperatures. The mid-December surface hoar/crust layer is typically down 60-120cm below the surface. The reactivity of this deeper weak layer appears to be quite variable but snow pack tests indicate that it still has the potential to produce large avalanches with open slopes at treeline areas being the greatest concern. The mid-Nov weak layer of crusts and facets can still be found near the bottom of the snowpack but has generally become inactive.