Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

7:30AM UPDATE: Downgraded avalanche forecast to Considerable, due to less precipitation overnight than expected. Human triggered avalanches are still likely, avoid all steep slopes and consider avoiding all avalanche terrain if you remotely trigger avalanches or see natural avalanches.  

Conditions are dangerous and you can die in an avalanche on Saturday. Anticipate unstable slopes and unusual avalanche activity, so avoid all avalanche terrain, including lower angle areas beneath steep slopes at mid and upper elevations. Avalanche activity will be very unpredictable - if you didn't trigger an avalanche in one spot, it doesn't mean you won't trigger a large avalanche that could kill you 10 feet further along. 

Problemi valanghivi

  • Storm Slabs

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

    Several natural, human-triggered, and remote small and large avalanches were reported to the north of us in the West North zone on Friday, where conditions are very similar to the West Central zone. We're getting more than a foot of new snow overnight, and avalanche activity will not be run-of-the-mill on Saturday. Avoid all steep slopes and the lower-angle terrain beneath them. We'll likely have a storm total of at least 3 feet of new snow, and human-triggered avalanches are very likely. You can still get out in the backcountry, just stay on lower angle terrain away from steep paths. 

    It's day 2 of a large storm after a long dry period. New slabs will form over a wide variety of questionable snow surfaces, including slick crusts, weak facets, or surface hoar. A range of old wind-affected surfaces exist as well. The usual strategies and tricks you use to manage risk may not be so reliable given the varying patchwork of old snow surface layers that could all react differently with the slab that forms over them.

    Some slopes may produce no avalanches or just smaller slabs like the ones we usually see the day after a storm. Other slopes, however, may produce large, unusual avalanches that propagate widely. They might release when you're in the middle of a slope, or you could remotely trigger them from a distance, possibly down at the bottom of the avalanche path where the avalanche will run out to. We expect you'll see large natural avalanches on Saturday as well, reinforcing the recommendation to avoid all avalanche terrain. 

    (1/31/2025)

    Touchy test slopes in the West North zone on Friday, with 6-16" crowns and propagating far. There were stiffer slabs in other spots that were more stubborn. 

    Photo: Pete Durr - USFS Backcountry Ranger

Avalanche Discussion

As of Friday evening, weather stations around the West Central zone received over an inch of water, which equates to over a foot of snow at upper elevations. This is only the start of the storm, and we can expect to see  over another foot by Saturday morning. Winds will be strong, and continued snow showers will occur during the day. 

The Cascades have gone through a period of dry and mostly cooler weather prior to Friday, the kind of weather that breeds weak snow. A week ago - during much cooler temperatures - near surface facets and surface hoar were growing large and surviving on all aspects.  A strong temperature gradient in the upper snowpack enabled faceting around and between a variety of crusts from the surface to 6-12" down to the crust buried on Jan 10th. One of the key traits of this mountain range is things just don't stay the same for very long.  Very warm temperatures, periods of strong wind, and plenty of sun did their best to degrade weak snow at the surface and put a lid on faceting below it. We're not sure whether those circumstances occurred this time, and avalanches may fail with more load on top down to the 1/10 crust. 

The take-home point is we do have the setup to have a much weaker snowpack than normal. But the reality is the amount of faceting and surface hoar below the new snow is going to vary widely across a forecast zone that is literally the size of a small state on the East Coast.  While some areas won't have much in the way of weak snow, others are flush with it. The best you can do is be conservative while the storm plays out, submit observations of what you see - or don't see - and let the pattern of avalanche activity become established over the weekend before stepping into bigger terrain.

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