Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

It is likely to trigger a wet or dry snow avalanche large enough to kill you on Monday, particularly if you are closer to the Cascade Crest. Some things to look out for are rainfall lower down, blowing snow higher up, sloppy wet snow you're punching deeply through, and cracking or collapsing in dry snow. Manage the complexity by defaulting to sheltered slopes that are not steeper than 35 degrees.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2

    Freezing levels hovered around 6000 ft on Sunday and will start to drop Sunday night. Another small round of snow is forecasted through the end of the day on Monday, accumulating higher totals closer to the Cascade Crest. The snowpack should, by and large, be dry at upper elevations. But whether you make it through all the wet snow lower down to reach dry snow higher up, conditions will not necessarily be safer. This atmospheric event (AR) is testing buried weak layers at all elevations with added weight to the snowpack, and we don't yet know how things have played out. Areas further west in the zone received and continue to expect higher snow totals, making conditions especially precarious in these areas.

    Persistent slabs can break in surprising ways and wider than expected. You will be more likely to trigger a slide in wind-loaded areas, so be on the lookout for signs of wind transport. Clear signs of instability are cracks shooting from your skis or machine, collapsing (whumpfing), and recent natural or triggered slab avalanches. The best way to manage this problem while we wait for the snowpack to adjust to its new load is to avoid avalanche terrain.

    (2/21/2025)

    A small skier triggered slab avalanche made clearly visible the two weak layer interfaces in the snowpack right now.

    Photo: Payton Schiff

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    Wet slab, persistent slab, wet loose, even glide—whatever you want to call them, liquid water has been and continues to be introduced to the snowpack, elevating the likelihood of avalanches. Until water has time to drain out or refreeze, avalanches will be of concern.

    It's possible a lot of avalanche paths where slides could grow large enough to kill you released over the weekend. However, we have very little certainty on this claim. Furthermore, new snow could accumulate in a start zone that previously released, making it hazardous again. Ultimately, we're not out of the atmospheric river yet, so with such uncertainty, enter into the mountains assuming conditions are still dangerous. Don't hang out on or below large paths if they have not slid yet. Cornices could be sagging and primed for breaking off, so be wary of precariously hanging blocks of snow above or below you. Don’t linger in terrain traps where avalanche debris can concentrate. If you find an avalanche path that has previously slid, be sure there is no lingering overhead hazard before entering it.

    (2/23/2025)

    Crown of a very large natural avalanche on the southwest side of Shukasan at about 5600'. (West North zone)

    (WS-N-D3-O)

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–1.5

    Sustained wind speeds up to 50 mph are forecasted overnight Sunday into Monday, accompanied by snow and dropping freezing levels. You'll likely find some new, dry snow transported by the wind. These slabs could be forming over slick crusts or an overall compromised (wetted) snowpack. Older slabs that might've formed overnight Saturday into Sunday could still have some lingering instability.

    Wind slabs usually form just below ridgelines and on exposed convexities and gullies, but with such strong wind, look for wind-affected snow lower down on slopes than usual. New slabs could be forming in paths that just released over the weekend, making them dangerous once more. Visual clues such as cornices, blowing snow, and drifted pillow-like dunes will help you identify where the wind has transported snow. Give cornices a wide berth when standing above and below them. If you see long shooting cracks from your equipment, new slab avalanche activity, or feel collapsing, choose more sheltered and lower angle terrain.

    (2/21/2025)

    The crown of a small skier triggered slab avalanche on Blewett Pass (02/21).

    Photo: Payton Schiff

Avalanche Discussion

We don't have a super clear picture of what has gone down in this zone over the weekend. A widespread small, wet loose avalanche cycle occurred on Blewett Pass, closing the highway for a few hours on Sunday. It would be safe to assume that further west in the zone where more precipitation fell, larger avalanches could have released and hit the valley floor. However, we have little other on the ground data to go off of. What we do have more certainty about is:

  • there are known weak layers in the snowpack
  • we are still in a very active weather pattern
  • the timing of wet slab avalanches is nearly impossible to predict

So, if you're still reading,  although we are probably past peak instability, it should be clear that we're not out of the weeds yet. Whether wet or dry, small or large, encountering an avalanche of some kind on Monday is likely. Avalanches will be most probable the closer to the Cascade Crest you are. As with any storm cycle, the snowpack needs time to adjust. Approach the backcountry with a healthy dose of skepticism on Monday.

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