Lawinenlagebericht

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 5 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

East wind is continuing to build new wind slabs that you’re likely to trigger near and above treeline. Older wind slabs can be found on windward aspects and still might be possible to trigger. You can avoid these avalanche problems by choosing terrain below treeline that’s less wind affected or avoiding avalanche terrain altogether. The less wind affected areas might also offer the best powder riding conditions. Be mindful of the single digit temperatures and much colder wind chill, it’s not a good day to get hurt in the mountains!

Lawinenprobleme

  • Wind Slabs

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

    Wind shifting from SW through N to E since Saturday built large and difficult to avoid wind slabs above treeline. You’ll also find some new wind slabs in wind affected areas around treeline. The most recent and mostly sensitive, formed in our current east wind, are largest and on aspects that aren’t typically wind loaded. Watch and feel for wind deposited snow, from slightly wind stiffened storm snow in somewhat sheltered and cross loaded terrain to thick, firmer slabs on directly loaded terrain above treeline. With variable wind slab all over the place, it’s a good day to be sure you have a route option that avoids avalanche terrain at middle and upper elevations.

    (2/21/2022)

    Small new wind slab that failed easily on a cross loaded test slope on Monday, 2/21/22. We expect similar but larger slabs today!

    Photo: Ryan Matz

  • Persistent Slabs

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

    The surface hoar layer that we keep talking about, now 1-2’ beneath the snow surface, seems isolated to open but sheltered terrain on middle and upper elevation north aspects. We’ve also observed weak facets near the January 12th crust that’s a few inches deeper and on similar aspects. We’re always wary in times like this when a new snow load is added to a persistent weak layer. You’re unlikely to trigger an avalanche on these persistent weak layers, but it’s not impossible. An avalanche in our storm snow might be able to step down to these deeper persistent weak layers.

Avalanche Discussion

Our 10-15” of new snow since last Thursday has since been affected by wind from nearly every direction. On Saturday, sustained moderate wind with strong gusts blew from the west and southwest, creating large wind slabs that are now stubborn on easterly aspects near and above treeline. Light wind from the north on Sunday allowed snow to fall with less wind effect before winds shifted east and ramped up Monday. East and southeast wind continues today with sustained speeds of 20+ mph and gusts pushing 40 mph. As a result, expect to find new wind slabs on lee terrain that vary from large but somewhat firm and stubborn above treeline to smaller and softer but reactive to touchy in slightly sheltered lee terrain. That’s in addition to the now stubborn slabs that formed on Saturday that we’re not ready to trust, though today’s wind may erode them away in some areas. We’re seeing wind affected snow in open areas at all elevations.

Below this mess of wind slabs, you’ll find a melt freeze crust formed on Valentine’s Day that’s thick on sunny aspects and low elevations and thin on upper elevation shady aspects. A few inches below this, the spatially variable surface hoar layer and facets near the January 12th crust are still worth keeping in the back of your mind. These weak layers seem isolated to north and east aspects. Our deeper snowpack seems consolidated and quite stable.

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