Avalanche Forecast

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Thursday

The next storm will bring snow and wind to the North Columbias late Wednesday into Thursday. Another system is expected Friday night. Each storm will bring a slightly warmer air mass driving the freezing level up the mountainside.WEDNESDAY NIGHT: Freezing level at valley bottom, strong to extreme southwest wind, 5 to 10 cm of snow.THURSDAY: Overcast, freezing level beginning at valley bottom rising to 1000 m, strong southwest wind at treeline, extreme southwest wind in the alpine, 5 to 10 cm of snow.FRIDAY: Broken cloud cover giving way to scattered cloud in the evening, freezing level beginning around 1600 m potentially rising has high as 2100 m, strong southwest/south wind at treeline, extreme southwest wind in the alpine, trace of precipitation. 5 to 10 cm of snow/rain at lower elevations on Friday night.SATURDAY: Broken cloud cover giving way to a few clouds in the evening, freezing level holding around 1300 m, at treeline expect moderate southwest wind initially, slowing to light wind near sundown, strong southwest wind in the alpine all day, trace of precipitation.

On Wednesday natural avalanches to size 3 were reported from the neighboring Glacier National Park region.On Tuesday storm slabs failed naturally and were sensitive to rider triggering to size 1.5 on all aspects between 1600 and 2700 m. Loose dry avalanches to size 1.5 were also observed. Avalanches were heard, but not seen coming from big alpine features.

The region picked up 20 to 60 cm of new snow with moderate to strong southwest wind Tuesday into Wednesday. The new snow rests on a buried weak layer (December 10th) that consists of facets, surface hoar, and a crust on solar aspects. Results on this interface are quite variable. It's very touchy in some places and less reactive in others. Lower in the snowpack, a pair of weak layers buried in mid-November are 30 to 110 cm below the surface. These layers present as surface hoar and a suncrust. They are most prevalent at treeline but may be found in sheltered alpine terrain too. While not recently reactive, this storm could push them to their breaking point. The most likely place to see an avalanche failing on this interface would be on south aspects at treeline where the surface hoar formed above a sun crust.At the base of the snowpack is a crust that formed near the end of October. Concern for this layer is dwindling but it may still be worth considering in places such as steep, rocky, alpine terrain, especially where the snowpack is shallow. It would likely take a large trigger such as a cornice fall to produce an avalanche on this layer.