Lawinenlagebericht

West Slopes South

Northwest Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Unstable snow from the recent storm continues to linger in many areas of the West South zone. This bucks our normal Pacific Northwest trends and rules of thumb. As a result, you may still trigger large avalanches on any steep open slope.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    Sure the storm ended Sunday, but the snowpack remains unstable. Observations from Crystal Mt, White Pass, Paradise (Mt Rainier), and nearby Mt Hood all showed buried surface hoar at the base of the new snow. While avalanche activity on this layer has been limited, several human-triggered slides at White Pass and Mt Hood, and a natural slide at Mt Rainier, seem to fit the description of this problem. You may find avalanches break above you or trigger remotely. While this weak layer seems to be healing, it still fails suddenly in snowpack tests. This indicates you could trigger avalanches if you are unlucky enough to hit the trigger point. Because it’s hard to tell exactly where buried surface hoar continues to linger, all steep open slopes should be suspect. Consider simply staying out of avalanche start zones even at mid and lower elevations.

Avalanche Discussion

While we’re used to “moderate” avalanche danger here in the northwest, the combination with a persistent slab problem makes a much more nuanced story. Basically, this isn’t your normal post-storm powder week. The snowpack continues to fail suddenly in tests and show the ability to produce avalanches. These persistent dangers are challenging to forecast, manage, and evaluate making us all more uncertain than normal, no matter the danger rating. So, consider taking a more conservative approach to your day’s plan. Slopes you might often travel during sunny days after a storm could be the exact place you want to avoid in these current conditions. 

NWAC forecasters and avalanche professionals observed buried surface hoar at the 12/8 interface at Cyrstal Mt, Paradise, and White Pass over the past week. While Mt Hood is a different zone, it currently shares a similar snowpack structure (and buried surface hoar). This leads us to believe Mt St Helens and Mt Adams also likely have this problem. It’s been several days since the last recorded or suspected avalanche. That’s good news. Similarly, snowpack tests are becoming harder to trigger. This is increasing our confidence. However, failures continue to show the ability to propagate and produce avalanches. One key item of note, this layer has been seen repeatably below treeline and on all aspects. So, this isn’t a localized issue. In fact, some of those steep open areas at lower elevations could be the most dangerous. 

Sunny weather this week formed a thin sun crust on steep southerly slopes. While this could make travel less pleasant in some areas, it currently doesn’t pose an avalanche hazard. Meanwhile, shaded slopes continue to hold on to soft cold dry powder.

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