Selkirk Mountains

Avalanche danger will increase throughout the day today as moderate to heavy snowfall builds a slab over very weak surface layers. Today your mountain travel mindset needs to change with evolving conditions; slopes that are safe this morning when you walk out the door will not be safe this afternoon. By closing bell natural avalanches will be possible and human triggered avalanches are likely. The storm favors the northern zones today with continued accumulation and winds over all zones through the weekend.

The long-awaited shift in weather has arrived, and with it we must reorient our mountain travel habits. We are emerging from a long period of cold dry weather that has morphed our upper snowpack into a deep layer of cohesionless facets topped with a widespread crop of surface hoar with various crusts and wind boards mixed in. During this sustained period of high pressure, we have become accustomed to small and isolated avalanche problems that have allowed us to travel confidently on all elevations and aspects. Today that all changes.

A significant winter storm enters our area today bringing with it a substantial load of warm moisture followed by an arctic front that is forecast to deliver between one and two feet of snow in the mountains over the next few days, with strong overnight winds. The initially warm snow will form a slab resting on top of notoriously weak layers, surface hoar and facets and a mosaic of crusts and wind board on various aspects and elevations. The exact nature of the layer interfaces matters less then basics of avalanche mechanics: slab over weak layers and a bed surface mean we have the recipe for avalanches.

The storm will initially favor the northern zones of our forecast areas with 8 to 10 inches of snow forecast to fall on the Selkirk and West Cabinets today. Silver Valley and Northern Bitterroots will lag behind with 3 to 5 inches today. Winds from the southwest will ramp up today from teens to 20mph range by this evening, and overnight gusts possibly exceeding 40mph.

The prospect of one to two feet of new snow has us all excited. But with the drastic change in conditions the avalanche danger will rise quickly, and we are likely to see a cycle of natural and human triggered avalanches. Going forward we need to change our mountain travel mindset from ‘free ride/open season’ to ‘cautious assessment’ as we enter a period of high uncertainty regarding size and special variability of the avalanche hazards. Allow time for the snowpack to stabilize and assess slopes carefully before committing to avalanchable terrain. I, for one, am looking forward to epic resort days and really fun low angle tree skiing in the days ahead.

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**We continue to receive intermittent reports of opening glide cracks and some failing naturally producing large to very large glide avalanches. Avoid traveling on or below slopes where a glide crack has opened. These types of avalanches are difficult to forecast when they will release.**