Lawinenlagebericht

Stevens Pass

Northwest Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

A storm will intensify throughout the day, and avalanche danger will increase as the day progresses. At first, your avalanche concerns may be limited to thicker wind-drifted snow deposits, but enough snow is expected by the afternoon that steep locations with more than about 6 inches of fresh storm snow are likely to avalanche with a human trigger.  Steer clear of steep slopes where new snow deposits are growing deeper, and especially in areas where the wind has drifted snow into thicker slabs, as those locations will be even more reactive. 

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    The day may start with Moderate avalanche danger, but you can expect the danger to increase to Considerable around midday. By the end of the day, storm totals are expected to reach around 3/4 of an inch of water, which will probably equate to just under a foot of snow. We're getting enough snow during the day that in non wind-affected areas, storm slabs are likely to avalanche with a human trigger. During the first half of the storm, temperatures are forecasted to increase, meaning we could see a bit of an "upside down" snowpack, leading to more touchy avalanche conditions. Thankfully temperatures will cool as the storm progresses, but don't expect the danger to decrease so quickly. Wind will ramp up and redistribute storm snow in exposed areas into wind slabs, which is where you will probably encounter the largest and most reactive slabs. Expect to find more of this as you gain elevation. During this storm it's best to play it safe and identify any locations where more than about 6 inches of storm snow exists, and avoid these areas on slopes steeper than 35 degrees. 

    A convergence zone may direct intense precipitation to the Stevens Pass area, and if this is the case, snowfall rates could be high, and shallow natural avalanches could occur during this time, as the snow struggles to adjust to the rapid change. Natural avalanches are possible with Considerable avalanche danger. This may also mean more snow than forecasted falls. Most avalanches will likely fail within the new storm snow, which will grow in size throughout the day. This means you could trigger an avalanche around 6 inches to a foot deep. However, there are a number of crusts and storm interfaces in the top couple feet where there's a small chance a failure could occur on one of those deeper layers. In general, a large variety of surfaces exist beneath the new storm snow layer we'll be getting. 

    Pay attention to red flags as your strongest indicators to avoid steep slopes. This includes recent avalanches, long shooting cracks, and whumphs. Other red flags include heavy snowfall and strong wind, both of which you could see on Thursday as well. When in doubt, stick to lower-angle slopes as the storm passes through. 

    (3/22/2021)

    Storm slab avalanches near Skyline ridge, failing with a human trigger 6" deep beneath the previous night's snowfall. This may be 2 years old, but it's probably very similar to what you might encounter on Thursday. On this day, you could trigger avalanches on most steep rollovers, but they were more reactive and propagated further with wind loading near ridgelines. 

    Photo: Irene Henninger

Avalanche Discussion

It's important to keep in mind that if you're in steep avalanche terrain and there's any chance you'll trigger an avalanche, make sure you've got a clean runout and an exit strategy in case you do trigger an avalanche. Even a small slide could be deadly or cause serious harm if you're on a slope with terrain traps. 

Observers reported a large snowboarder-triggered slide on a steep, wind-loaded Southeast facing slope near Cowboy Mountain on Tuesday. The slide was approximately 70ft wide and 2.5ft deep, running on a crust that was suspected from mid-February (the Valentine's Day Crust, or Superbowl Crust, depending on your preference). WSDOT also completed mitigation along the highway on Tuesday and triggered a number of small slides. There was one larger slide, triggered using a large explosive, that was fairly wide and over 2ft deep. This slide may have run on the same crust as the snowboarder-triggered one. The debris covered all four lanes of Hwy 2.

 

 

 

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