Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Several human triggered avalanches, including a partial burial, occurred in neighboring zones in the last three days. More snow overnight and through the day Monday will keep human-triggered avalanches likely. Avoid steep areas where thick slabs of snow are present, and steer around lower elevations steep slopes if you notice the snow getting wet and small rollerballs are seen coming down. 

Avalanche problems

  • Storm Slabs

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

    Several human-triggered avalanches occurred in the last 3 days in neighboring zones, including a group of backcountry skiers triggering and getting caught in a slab avalanche in the West North Zone on Sunday, partially burying one. Luckily, they walked away unscathed. We appreciate their sharing so that we can all learn from it, and you can check out the observation HERE.  Previously, avalanches remained specific to wind-loaded areas, and they were touchy. A few were reported on Sunday, but warmer temperatures made the snow heavier and not as reactive for slab avalanches. So far, most avalanches were not large enough to bury a person, but more snow is falling Sunday night and all day Monday.

    It is likely that you can trigger a larger avalanche Monday, one which could be big enough to bury and kill you. Locations will not be as isolated as in the previous days. Rather than small pockets, you could find larger slopes of unstable snow. They may exist as reactive slabs in non-wind loaded areas, however, they will probably remain most reactive in areas where the wind redistributed snow into thicker deposits, as moderate to strong winds will continue shifting snow around. You might find slabs farther downslope and on cross-loaded features in addition to just below ridgeline. Poor visibility or a layer of new snow could make slabs harder to pick out in the terrain around you. Monitor new snow depth you as gain elevation and change aspects. Don’t ignore obvious signs of instability like shooting cracks or even subtler clues like a change in snow depth or texture. Evaluate each slope on a case-by-case basis and travel on lower angle or wind-scoured terrain to reduce the likelihood of triggering an avalanche. 

    It is likely that you could trigger a storm slab avalanche Monday. Pay attention to obvious clues such as cracking, visible in the top right. 

    Photo: Alpental Pro Patrol

  • Loose Wet

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

    Wet loose avalanches became the primary concern on Sunday, with more than we thought we would see occurring. This is probably moreso the case in northern areas closer to highway 20 than souther portions of the zone as more lower density new snow is present there. Ones in the West North Zone were mainly small (D1), but there were some large (D2) avalanches, running in the new snow layer. This time of year we can almost expect to see wet loose avalanches most days. Springtime radiation balances are tough to hit right, so it becomes a bit more difficult to predict these avalanches this time of year. If snow surfaces were previously low density and dry, then just a little sun- or a warm, humid cloud like we saw Sunday- could tip the scales and avalanches will result.

    Temperatures are forecasted to remain a little cooler than Sunday. You can primarily expect to encounter these avalanches in near treeline areas where the fresh low-density snow fell, moreso than below treeline elevations where much of the snowpack is old and previously rain-affected snow. There's a chance these avalanches could occur at higher elevations if it warms more than forecasted. Temperatures will peak in the evening, so expect an increase in this danger throughout the day. You may find rollerballs or small natural wet loose avalanches, triggered from tree-bombs or from near steep and rocky areas. You might be able to trigger one, starting small and then fanning out, as you move across a steep slope. If you encounter wet, sticky snow or signs of small natural avalanches, avoid steep slopes in nearby areas. 

    (3/13/2022) Small wet loose avalanches occurred naturally and with human triggers on Sunday. Photo: Jason Speer

Avalanche Discussion

Snow surfaces were reported as becoming moist and heavy Sunday into near treeline elevations. Observers noted that slab avalanches were more difficult to trigger, although wet loose avalanches took over as the main problem. Around a half inch of water (possibly 6 inches of snow) overnight will fall on top of this layer, and another 6-12 inches will fall during the day. With snow becoming more stubborn Sunday, avalanches may remain limited to the new snow that falls Sunday night and Monday, but there is a possibility that avalanches could run deeper at higher elevations where not as much warming occurred Sunday. 

New snow layers are building on a variety of surfaces including sun crust, dry and weak snow in shady, wind-sheltered terrain, old wind slabs, and wind-scoured surfaces. Weak, faceted snow continues to be found around the Cascades around the old snow surface buried on March 8th. Besides the previously mentioned snow surface and new snow layers, the upper snowpack is generally strong with no layers of concern. It is unclear how reactive this newly fallen snow will be. Travel conservatively, starting on small slopes, and paying attention to existing avalanches and other obvious clues such as cracking. With all the uncertainty and a bunch of new snow, consider leaving that steep slope you've had your eyes on for another day. 

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