Avalanche Forecast

Brrrrrr! Cold and dry conditions persist under arctic air

Sunday night: Partly cloudy, moderate northwest ridgetop wind, alpine temperature -18 C.

Monday: Mix of sun and cloud, light northwest wind, alpine high temperature -20 C.

Tuesday: Mainly sunny, light north wind, alpine high temperature -23 C.

Wednesday: Mainly sunny, 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 possible to trigger. At treeline elevations and below, avalanches may be remotely triggered and break larger than expected on a reactive layer of surface hoar. 

No recent avalanches have been reported. On Thursday, operators were able to trigger small (size 1-1.5) avalanches breaking within the recent storm snow with explosives. 

On Wednesday, a skier remotely triggered a size 2.5 persistent slab avalanche from a ridgetop near Quartz Creek. This avalanche failed on a weak layer of surface hoar on a slope near treeline. Observers across the region this week reported additional signs of instability on this layer including cracking and whumphing near KHMR and propagation in snowpack tests near Mt. Pat.

5-15 cm of new snow since Friday with moderate to strong northwest winds has formed fresh wind slabs in lee features at upper elevations. In sheltered areas, cohesion-less snow may be prone to dry loose avalanches that can run far and fast in the cold, dry conditions.

The snow from the past week is settling over a very weak layer of surface hoar buried 50-80 cm deep. This persistent weak layer has potential to surprise backcountry users with how wide the fracture can travel across slopes. Recent avalanches on this layer have primarily been reported at treeline and below in the northern half of the region. This layer will be slow to gain strength and requires careful terrain selection.

Down 60-100 cm, an older layer surface hoar and/or a thin melt crust from mid January can be found. This layer was more prominent in the north of the region in sheltered, open slopes at treeline.

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.
• Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
• Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.