Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

An approaching storm will bring up to 2’ of new snow and strong winds. Avalanche danger will increase overnight and throughout the day. Plan on starting - and probably finishing - your day in simple, lower-angle terrain with limited exposure to big slopes above. Avoid being on or under all avalanche terrain if you see widespread signs of instability like shooting cracks or natural avalanches. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    Sunday won’t be a day to sneak around big avalanche terrain. Dangerous conditions should continue through the day as long as the snow keeps piling up and winds keep blowing. It’s up in the air if we will see a cycle of large natural avalanches. But the setup is in place with new snow and wind slabs forming over a snow surface that weakened (as in facets and surface hoar) since the last storm.

    Heavy snowfall in West Central might hold off until mid-morning when convergence zone-enhanced snowfall starts to kick in, especially in and south of the Mountain Loop. Don't get lured into big terrain just because snow totals in the morning are less than anticipated. Heavy snowfall will show up sooner or later and stormy conditions will hang on longer in West Central and the Passes than other zones.

    You are more likely to trigger an avalanche in wind loaded terrain but there should be enough new snow that all slopes should be considered suspect. Blowing snow should clearly show you which slopes are the most susceptible to triggering an avalanche. If you find sheltered terrain with deep uncohesive new snow then dry loose avalanches are the next hazard you need to contend with.

     

    Example of widely propagating, storm slab avalanche in treed terrain. Swift Creek in April 2022. 

Avalanche Discussion

Sunday’s forecast seems like it should be a slam dunk but as usual some questions remain. If the bulk of snowfall and strong winds come overnight and then taper in the morning, travel around and even in smaller avalanche terrain could be a reasonable proposition by day’s end. If heavy snow showers and strong winds persist then the rating is effectively High and all avalanche terrain will be a no-go. The potential for larger, widely propagating avalanches releasing at the old snow surface of facets or surface hoar adds another layer of uncertainty. The best policy will be to plan on a mellow day and default to terrain with little to no exposure to avalanches.

Avalanche danger is rated Considerable at all elevation bands. It will be more dangerous in upper elevation, wind exposed terrain. Heavy snowfall at low snow levels means typically “safe” terrain might be a bit more heads up than usual.

In West North winds ramped up ahead of the storm with gusts in the 50's by late afternoon. Shallow but reactive wind slabs were found on leeward slopes and signs of wind effect were commonplace in exposed areas. There were two reports of backcountry travelers getting caught and carried in shallow wind slab avalanches in the afternoon. These occurred on Mt. Ann and also near Ptarmigan Ridge.  Less wind and no new wind slab avalanches were reported from either Stevens or Snoqualmie Pass.  

 

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