Lawinenlagebericht

Olympics

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Rainfall and warmth increase the risk of isolated large wet avalanches at middle and upper elevations, and these avalanches could be surprising.  Evaluate slopes for water pooling above crusts before engaging with large, steep open slopes. Limit your terrain selection further with evidence of recent avalanche activity.

Lawinenprobleme

  • Wet Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2

    Moderate rainfall Saturday night will push the wetting front into layers of dry snow and there is a chance of water pooling on crusts that exist on specific aspects. If this occurs, natural wet slab avalanches become possible. The distribution of potentially concerning crusts 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. If moderate precipitation occurs as forecast Saturday night, steer around steep slopes that have a firm underlying crust. 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 should have you quickly adjusting your terrain selection to avoid avalanche terrain.

    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 0.5" of water equivalent, but the risk is that it doesn't and that wet slabs conditions develop. Photos in the gallery depict a low-elevation snowpack that is shallow and already well adjusted to the spring-like weather.

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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