Avalanche Forecast

Brrrrrr! Cold and dry conditions persist under arctic air

Sunday night: Partly cloudy, light northwest wind, alpine temperature -25 C.

Monday: Mix of sun and cloud, light northwest wind, alpine high temperature -25 C.

Tuesday: Mostly clear, light north wind, alpine high temperature -26 C.

Wednesday: Mostly clear, light north wind, alpine high temperature -26 C.

Three different flavors of avalanches may be possible on Monday. Expect loose dry avalanches in steep areas where the recent snow has not formed a slab. Although typically small (size 1-1.5), these avalanches pose a serious concern for ice climbers and for people traveling in extreme terrain where the possibility of getting knocked off of your feet has severe consequences. At upper elevations, newly formed wind slabs may be reactive to human triggering. At treeline elevations and below, avalanches may be remotely triggered and break larger than expected on a reactive layer of surface hoar. These MIN reports from Chappell, White River, and Allen Creek from this past week are great examples of the potential for avalanches to propagate wider than usual due to this weak layer. 

Note: We currently have very few observations from this region. Please consider sharing what you see by submitting a MIN report.

Incremental snow and ongoing winds have formed fresh wind slabs in lee features at upper elevations. With up to 25 cm of low density snow over the past several days, cohesion-less snow in sheltered areas may be prone to dry loose avalanches that can run fast and far in these cold, dry conditions.

The snow from the past week is settling over a reactive weak layer of surface hoar buried 40-70 cm deep. This persistent weak layer has potential to surprise backcountry users with how wide the fracture can travel across slopes. Avalanches on this layer have primarily been reported at treeline and below. Although avalanche activity appears to be decreasing, this persistent weak layer will be slow to gain strength and requires careful terrain selection.

A second weak of layer of surface hoar from mid January is down around 70-110 cm and is most prevalent in sheltered, open slopes at treeline and below. 

Deep persistent weak layers can still be found in the lower snowpack. These weak layers are most likely to be triggered from rocky areas with a shallow or thin to thick snowpack.

• Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
• Stay off recently wind loaded slopes until they have had a chance to stabilize.
• Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.