Bollettino valanghe

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Northwest Avalanche Center
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Pericolo valanghe

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Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Steer around steep slopes near ridgelines where you find wind-stiffened snow.  Soft snow conditions on the northerly half of the compass overlap with the continued low-likelihood/high consequences of triggering a deeper persistent slab avalanche at middle and upper elevations. 

Problemi valanghivi

  • Wind Slabs

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

    Cold temperatures and NE winds formed shallow wind slabs midweek near and below ridgelines.  Winds will shift to the W-NW and may start to move snow onto more traditional lee aspects.  Steer around steep slopes below ridgelines where you find new or recently wind-stiffened snow. 

    Shooting cracks and, of course, natural or human-triggered avalanches in wind-drifted snow are obvious signs to avoid similar steep slopes.  While wind slabs avalanches will likely be shallow, consider the consequences of a small avalanche stepping down and awakening a larger avalanche (see below). 

    Shooting cracks in freshly drifted snow are a sign that you can trigger a wind slab avalanche in nearby steep slopes. 

    Photo: Joe Dellaporta

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2

    Backcountry travelers in the Hurricane Ridge backcountry reported whumpfs on our Persistent Weak Layer 1-2' below the surface last Sunday and Tuesday.  A weak snowpack structure exists on the northern half of the compass, but the structure is variable throughout the terrain and in other places, lacks a slab above the weak layer.  Your Cascadian neighbors have seen the # of persistent slab avalanches decrease over the last 2 weeks, along with more inconsistent snowpack results targeting similar weak layers.   

    That doesn't mean the problem has gone away, only that it's more isolated throughout the terrain and harder to trigger.  If you experience whumpfs or collapses, retreat to lower angle slopes without overhead hazard.  Cornice fall or a smaller avalanche (see above), could trigger a deeper and more widely propagating avalanche on the same slope.  As we head into the latter half of the weekend with new snow and warmer temperatures expected, this problem may become front and center once again.   

    (2/2/2025)

    A widely propagating slab avalanche on a North aspect in the Maggie's area.  A shooting crack on the same slope shot out a whopping 40'.  While this avalanche occurred during a storm cycle, it likely failed on the persistent weak layer we're still tracking. 

    Photo: Anthony Anglikowski

Avalanche Discussion

Hurricane Ridge climbed out of the freezer on Wednesday, with temperatures pushing above 20F for the first time since Feb. 8th.   On Thursday, NPS Rangers reported that the cold weather had maintained excellent snow conditions on north slopes.  NE winds had built shallow but sensitive wind slabs just below ridgelines. Despite the cold weather, sunny weather had formed a sun crust on southerly aspects, making for less than pleasant travel conditions.  Weak snow (facets) are sandwiched between a series of crusts (1/10 and 1/29) 1-2' below the snow surface on shaded aspects.  In some areas, there may be a very thin layer of facets above the upper crust.  This crust/facet complex is the likely culprit of a series of widely propagating, human triggered avalanches during the 2/1 - 2/2 weekend and a series of whumpfs last Sun and Tue.   We are going to keep warning about this interface as we head into a holiday weekend with new snow and warming temperatures.  

Share your observations with the community and NWAC. Even if you didn't see an avalanche or a snowpack test, your information is incredibly valuable.  Every afternoon, 4-5 NWAC forecasters from around the region meet to discuss the latest snowpack and avalanche observations, and weather forecast to create the next day's avalanche forecast.  We look at information from the public, other snow professionals, and weather station data to round out our picture.  Share early and often!

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