Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

A winter storm bringing heavy snowfall and strong winds will increase avalanche danger overnight and into Sunday. At upper elevations, you can trigger avalanches in deep drifts or where new snow falls on slick crusts. Consider sticking to wind sheltered terrain and avoid steep slopes in alpine areas. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Snow totals from this storm are likely to taper significantly from west to east. Areas near the Cascade Crest, such as Salmon La Sac and Holden, may pick up over a foot of fresh snow, while Mission Ridge may only squeeze out a few inches. The strong winds accompanying this storm will build large and dangerous slabs near ridgelines in alpine areas. New snow and wind drifted snow will fall on various surfaces, including slick crusts, bare ground, and possibly older weak snow from mid-November. This variability leads to uncertainty about how the new snow will bond to underlying surfaces. With increased uncertainty, it is important to approach new terrain slowly and observe changing conditions as you gain elevation. You can use quick hand pits and small rollovers in terrain to monitor how the new snow is bonding to the old snow surface. Look for red flag signs of instability, recent avalanches, a collapsing snowpack beneath you, or shooting cracks, as these are sure signs to travel on lower angle terrain. 

     

    Shooting cracks like these coming from skis, snowshoes, snowmobiles, feet, etc are indicators that reactive slabs exists.

    Photo: Lee Lazzara

Avalanche Discussion

Access to many areas of the eastern Cascades is challenging, and we have limited information about the snowpack. This storm will likely begin as rain for locations below 3000ft, and while this storm may improve conditions slightly, access will remain challenging. If you are headed out into the mountains this weekend, be prepared for long approaches on thin snow cover. Many motorized trailheads have limited snowpack, and most have yet to begin grooming operations. New snow may shallowly bury rocks, stumps, creeks, or other hazards at upper elevations. 

Many areas on the eastern slopes of the Cascades enjoyed an early start to winter at the beginning of November, receiving 8-10" of snow down to valley bottoms. Prolonged, cold, dry weather followed this storm which transformed this snow into weak, angular, sugary snow crystals. During this dry weather, inversion conditions warmed upper elevations, and strong winds drifted this weak snow around. We received many observations of large surface hoar growth in lower elevation locations sheltered from the sun and wind. This storm may bury this layer 10-20inches deep. While warm temperatures over the last 24hrs have helped to strengthen and round these snow grains, we still have a lot of uncertainty about the extent and distribution of this weak snow layer. Mission Ride Ski Patrol reported that the snowpack was still weak and faceted in and around the ski area. When traveling on sheltered northern aspects, it is important to dig down and determine if this persistent weak layer exists beneath the new snow. Avoid traveling on steep terrain if you find a weak sugary layer of snow beneath the storm snow or feel the snowpack collapse beneath you. 

Are you going to take advantage of the new storm snow? Let us know what you find by submitting an observation.

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