Bollettino valanghe

Olympics

Northwest Avalanche Center
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In sintesi

7:30 AM update: Due to heavy rainfall Saturday night

Significant amounts of water moving through the snowpack will impact previously dry snow layers. The result could be large and surprising natural avalanches. Seek slope angles less than 30 degrees with limited overhead hazard to stay safe.

Problemi valanghivi

  • Wet Slabs

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    Update: Wet slabs could be widespread in middle and upper-elevation terrain. They may fail without warning and could exist on any aspect. Seek slope angles less than 30 degrees until we are confident the snowpack has adjusted to a more liquid state.

    The most concerning crust with the potential to pool water and lubricate the bed surface of a wet slab exists primarily on N aspects at middle and upper elevations, but we can't rule them out on other aspects. Wet slabs are a tricky problem to handle because they can occur with no warning. You can dig down two feet into the relatively shallow snowpack and make sure that you don't find water pooling on a crust. Just be aware that any test may not be representative of different aspects or elevation bands. Any evidence of large wet avalanches confirms the problem.

    You're more likely to encounter small wet loose avalanches than wet slabs, but these will be somewhat easier to manage. You can trigger them on a steep slope approaching 40 degrees at any elevation anywhere you can sink into the snow past your ankle. These will be most impactful above terrain traps such as rocks, trees, or cliffs. 

    Example: Wet slabs can even occur on smaller features but propagate very widely. 

    Photo: Dallas Glass

Avalanche Discussion

The snowpack at Hurricane Ridge has been handling the warm temperatures and rainfall gracefully thus far.  Warm temperatures and rainfall starting Friday, with 0.25" of rainfall so far in this storm cycle. The rain produced a shed cycle of snow off rocks, cliffs, and trees. 

NPS staff found around 20 inches of pencil-hard snow above a knife-hard crust at 5200 ft on a N aspect at Hurricane Ridge.  Other aspects have a more sporadic distribution of crusts that may or may not be able to pool water. That pencil-hard upper snowpack is likely to absorb some of the recent rainfall, but the risk is that it can't handle the 1.4" of water that fell Saturday through Saturday night. Photos in the gallery depict a low-elevation snowpack that is shallow and already well-adjusted to the spring-like weather.  However, we've adjusted lower elevations to moderate danger out of an abundance of caution.

NWAC observer Kaitlin and NPS staff were out in the Steeple Rock area Thursday.  They found a snow-line around 4500' and 4" of heavy new snow above a supportable crust.  During the work week, small shots of new snow and oscillating snow-lines had led to several rounds of rollerballs and small wet loose avalanches on all aspects.  The upper snowpack consists of a series of crusts and drier snow that could become ingredients for larger wet avalanches later into the weekend.  Near and just above 5000', they found snow depths ranging from 1' to 4.5' depending on the aspect and exposure. Lower elevations and areas with low snow depths will likely have significant melt-out as the warm wet weather drags into next week.  

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