Bulletin d’avalanche

West Slopes South

Northwest Avalanche Center
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Danger d’avalanche

Thu
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré last year. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Strong winds drifted the recent snow into thick and reactive slabs, making human-triggered avalanches likely. Look for signs of wind effect like textured surfaces and pillowy deposits and avoid steep open slopes where you see them. Sunshine and warming will add to the hazard so give a wide berth to steep sunlit slopes, whether they are wind-loaded or not. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2.5

    1-2ft of fresh snow was hammered by the wind on Tuesday, resulting in widespread hard and soft wind slab avalanches. Wind-affected snow will be found at all elevation bands and below tree line on Wednesday. Look for signs of wind effect in the usual locations like below sharp ridges and cliffs and at the tops and sidewalls of gullies, but also in treed terrain and below mid-slope rollovers. Cracking and collapsing are obvious signs of instability and hand pits, uptrack tests, and small test slopes can all be used to help gauge slab behavior. Keep in mind, however, that it can be hard to find a representative test slope that has the same conditions as the slope you are eying and you may not see any obvious red flags. Hard slabs are especially problematic as they can let you well out onto the slope before releasing, break above you, and propagate widely around terrain features. 

    The best bet on Wednesday is to avoid steep slopes wherever you see signs of wind-blown snow. This approach will also steer you towards more enjoyable riding conditions.   

    (2/25/2025)

    A widely propagating hard wind slab avalanche at Crystal on Monday. This slide was triggered by a ski patroller from the ridge and was up to 3 1/2' deep.

    Photo: Andy Harrington

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    New snow will see the sun for the first time on Wednesday. Look for fresh wet avalanches, rollerballs, pinwheels, and sinking in past your boot tops into moist snow. If you see any of these signs, it's time to switch to a shady slope. Be aware of what you are below as snow may shed off rocky faces before the surface you are on shows signs of moistening. With so much fresh snow on the surface, some avalanches could gouge deeply and run far. Wet loose avalanches could also act as a trigger for deeper slab avalanches.

    (2/23/2025)

    Wet loose avalanches were observed by NPS rangers near Paradise.

    Photo: NPS Rangers

Avalanche Discussion

Since this cycle began, between 4.3 and 6.7" of total precipitation has fallen. While much fell as rain, the final act brought a much-needed refresh of snow above about 4000ft. New snow totals ranged from 10-20" (1-2" SWE) and the winds ripped. White Pass won the sweepstakes with a maximum gust of 116 mph! Crystal Mountain Pro Patrol reported reactive to touchy and widespread storm and wind slab avalanches. Many of these were large, deep, propagated around terrain features, and occurred well down the slope. A snow professional noted a natural wind slab avalanche on Crown Point, while NWAC forecasters found sensitive pockets of soft storm slab in sheltered terrain that popped off easily at roll overs. While we expect the storm slabs to have mostly settled out, they could pose an issue on steep and unsupported slopes. Between the warm temperatures and the hammering winds, the snow surface will be a mixed bag on Wednesday.

It's almost March and the sun is strong! While some slabs may start the day as stubborn, we are uncertain as to how they might react to warming. On top of that, the snowpack has been hammered by liquid water and snow and it hasn't fully adjusted to the load, nor has all of the water frozen or finished its journey through the snowpack. Though the JDL and 1/10 are mostly out of sight and out of mind, until the snowpack is fully locked up above them, we can't totally write them off. 

Régions couvertes