Lawinenlagebericht

Stevens Pass

Northwest Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Friday won’t be a typical storm day. Anticipate unstable conditions and unusual avalanche activity. Stick to low-angle, conservative terrain that limits exposure to slopes that could produce avalanches.   

Lawinenprobleme

  • Storm Slabs

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

    The most dangerous areas will be shaded northerly aspects, especially on leeward slopes at middle and upper elevations. Widespread weak facets on the old snow surface could make avalanches easy to trigger and they could break widely across terrain features. 

    The usual strategies and tricks you use to manage risk might not be so reliable given the variation in snowpack structure below the new snow. Some slopes might produce no avalanches or just the small slabs you might normally expect. Other slopes could beget unusual avalanches that propagate widely, release when you are in the middle of a slope, or might even be triggered from below.

    (2/24/2021) An example of a widely propagating avalanche in new snow from a previous season. Rock Mtn. SE, 5,800ft.  Photo: Josh Hirshberg

Avalanche Discussion

A major storm will bring 1 foot of snow by the end of Friday. Southwest winds will be strong enough to drift snow at ridgetops. The storm will continue into the weekend.

You can keep your decision-making simple and enjoy the fresh snow in low-angle terrain. If you choose to venture into avalanche terrain, there's a huge range of variable old snow layers to consider. If you find the following, consider avoiding avalanche terrain:

  • The facets (and surface hoar) mentioned are above are the most obviously dangerous weak layer. You can find them on all northerly aspects, as well as, some shaded east and west aspects.
  • If you find buried surface hoar with no underlying facets, you'll be dealing with a uniquely dangerous scenario.

Other old snow surfaces include:

  • The surface of sun-exposed, southeast through southwest, as well as some east and west aspects, have transitioned to melt forms. You'll likely find slick crusts, which may not bond well to the new snow.
  • Some of these slopes may hold unfrozen or still moist melt forms.

 

For the past couple weeks, we've been tracking surface conditions. On Thursday, an NWAC forecaster in the Lichtenberg and Valhalla Lake area found softening crusts on sunny slopes and large (up to 2mm) facets on the surface of shaded slopes. On the 29th, an NWAC forecaster investigated steep, south aspect on Cowboy Ridge and found that the top 3 feet of the snowpack had turned to melt forms. See other observations from last weekend here and here. 

If you get out in the mountains, let us know what you see by submitting an observation HERE or via the Avy App. 

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