Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Heavy snow and strong winds will continue to pummel the volcanoes, resulting in natural avalanches. Travel in avalanche terrain is not recommended in these areas. Elsewhere, you’re likely to trigger an avalanche on slopes over 35 degrees, especially if it's wind-loaded or unsupported. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3

    We expect widespread natural avalanche activity to continue on the volcanoes while other areas will be primed for human-triggered slides. However, naturals could still occur away from the volcanoes, especially in the morning hours. In isolated locations, avalanches could step down into old snow layers and grow very large or descend toward valley bottoms.

    Several waves of precipitation, fluctuating freezing levels, and strong winds have resulted in a layered upper snowpack throughout the zone. You’ll need to check the recent storm snow for weak interfaces and its bond to the old surface by digging. Small test slopes and uptrack tests won't cut it when the snow is this deep. Depending on your location, there could be several feet to investigate. Heavy snow over soft snow, layers of weak grains such as graupel, or wind-drifted slabs hidden below the surface are just some examples of potential failure points. Slabs should be larger as you ascend in elevation or in wind-loaded terrain. You’ll need to contend with storm slabs, wind slabs, and loose avalanches as you pick your way through the mountains. Regardless of the avalanche problem, you’re more likely to trigger one on slopes over 35 degrees.

    Widely breaking slabs at the base of cliffs on the west side of Mount Adams last week. Large to very large natural avalanche activity is expected to continue on Thursday. 

Avalanche Discussion

As is often the case, the volcanoes are driving the hazard in the West South zone on Thursday. Continued snowfall and heavy winds overnight will result in a fresh round of slabs. We expect more natural activity on the volcanoes, but that doesn’t mean it’s not dangerous elsewhere. It has been a very active weather week, and feet of new snow has fallen on a suspect snowpack. You’ll need to evaluate terrain carefully and should default to avoiding slopes over 35 degrees until the snowpack has had time to heal.

Although less snow has fallen near the crest, a weaker snowpack exists there. Before this storm cycle, a series of crusts interspersed with pockets of weak snow existed above the Early February Crust (EFC). NWAC forecasters have found weak grains sitting on the EFC as recently as Wednesday near Crystal Mountain. Avalanches on these layers have been reported by the Crystal Mountain Pro Patrol during their mitigation efforts in recent days. Other very large avalanches this past week have been reported on the volcanoes, some breaking widely or wrapping terrain features.

After such a snowy week, snow immersion suffocation (SIS) can be a real hazard. Keep your partners in sight and know the risks. You can learn more here.

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