Lawinenlagebericht

West Slopes South

Northwest Avalanche Center
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Lawinengefahr

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

Rain, warm temperatures, and sunshine by Tuesday afternoon will thaw the snowpack and create dangerous avalanche conditions. Wet avalanches could grow large, cornices may fall, and it's uncertain how lingering weak layers will handle the rapid change. Build in a wide margin for error with these complex conditions and choose conservative, low-angle terrain.

Lawinenprobleme

  • Loose Wet

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

    Light rain will continue to fall well into the alpine overnight Monday, especially on the southern volcanoes. Expect cloudy skies early Tuesday as conditions dry out, and increasing sunshine in the afternoon as freezing levels skyrocket to 9500ft. As the recent dry snow becomes wet and saturated it will rapidly lose strength. You may see both wet slab and wet loose avalanches that could gouge into the snowpack, build significant mass, and run far downslope. A wet slide in motion could even trigger deeper weak layers resulting in a much larger and destructive avalanche. When you find wet sticky snow or see new avalanches, dial it back and stay off of and out from under steep slopes. We expect most of the natural avalanche activity to stay small, but you could see a larger avalanche in big complex terrain and where more snow accumulated over the past few days.

    (3/1/2022) Example: A wet slab avalanche from our last rain on snow event.  Photo: Dallas Glass

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–2.5

    It’s hard to say exactly how the persistent weak layer will react as the snowpack thaws. It will be best to step back during this rapid change and steer clear of upper elevation start zones. Cornices could even fall acting as huge triggers on slopes below. Avalanches this past week have been remotely triggered from adjacent terrain and ridgelines. So, put plenty of room between you and any steep open slope on W-N-E aspects near and above treeline.

    (3/17/2022)

    A large avalanche that failed on 3/16 near Crystal Mountain. This slide failed on the 3/8 facets and ran on the Early March Crust, with debris crossing a popular traverse track.

    Photo: Robin Pendery

Avalanche Discussion

Observers early Monday enjoyed their last powder turns before snowfall transitioned to rain. The warm-up increased the sensitivity of storm slabs and caused widespread wet loose activity near and below treeline. Snow totals over the past 24 hours vary throughout the zone with 5-8in near White Pass and Crystal and over 1ft at Paradise. The more recent cold powder, the more snow there will be to entrain as wet avalanches run in the coming days. Wet avalanche activity may peak during the rain overnight Monday, or could be ongoing with warming and sunshine throughout the day. Regardless, the snowpack will need time to adjust, and Tuesday will not be a day to mess around if you venture out into the backcountry.

Over the past several days, human-triggered avalanches and audible whumpfs have been observed across the West South zone. A layer of sugary facets just above the Early March Crust has been the culprit in all of these events. In most locations, this layer is now 2-4ft below the surface. While this may make it harder to trigger, any resulting avalanche could easily be big enough to bury and kill you. Unfortunately, there aren’t a lot of ways to easily rule this avalanche issue out. Tracks on a slope and a few snowpack tests do not mean it's safe. Best to just give this hard-to-manage problem the respect it deserves. 

At lower elevations, less snow will limit the size of avalanches. Instead, you may find sticky snow, firm rough surface, open creeks, and piles of avalanche debris.

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