Lawinenlagebericht

Banner Summit

Sawtooth Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
4 · Gross
Waldgrenze
4 · Gross
Unterhalb
4 · Gross
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Kernpunkte

Heavy, wet snowfall, valley rain, and strong winds are creating very dangerous avalanche conditions, from the mountain tops to the valley floor.  Widespread avalanching is likely to occur. Some will be large enough to snap trees or destroy a wood-frame house. Stay off of and out from below steep slopes—slopes steeper than about 30 degrees. Avalanches may be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes. 

The backcountry Avalanche Warning does not apply to the HWY 21 avalanche program.

Lawinenprobleme

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    2–3

    You are very likely to trigger a large, destructive persistent slab avalanche. Today's wet and wild storm—with heavy, dense snowfall, valley rain, and strong winds—is overloading a snowpack with multiple weak layers. As the storm progresses, these layers will be buried beneath a dense 3-5' thick slab. Any slide you trigger could be large enough to not only take you out, but also the vehicle you drove to the trailhead, the house you woke up in, and possibly the forest in your backyard.

    Yesterday, riders in the White Clouds remotely triggered a large avalanche while riding in flatter terrain an estimated 1/4 mile away (photo above/right). It appears to be 2-4' thick and likely failed on weak, faceted snow buried in November. Let me be clear: this avalanche was triggered before today's storm. 

    Avoid traveling on or beneath all avalanche terrain today—slopes steeper than about 30 degrees.  Avalanches are likely to release naturally and could reach the valley bottoms. Pay close attention to the slopes above you and don't travel in the runout zones of avalanche paths.

    (12/26/2022) In the nearby Galena Summit & E Mtns Zone, snowmobilers remotely triggered this large avalanche on Monday in the White Clouds while riding in flatter terrain an estimated 1/4 mile away. Above Washington Lake, 10,500', E-NE.

  • Loose Wet

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

    Adding insult to injury, natural and triggered avalanches are very likely to occur within the accumulating storm snow. Even without the buried weak layers described above, avalanche conditions would still be dangerous. Storm slabs will be most common on middle and upper elevation slopes that are getting drifted by today's strong winds, but could also occur on steep, wind-sheltered slopes. Lower and middle-elevation slopes at the snow/rain line may be particularly susceptible to storm snow instabilities. These avalanches could trigger deeper weak layers (described above), producing much larger avalanches.

    WET SNOW AVALANCHES: Somewhat secondary to the problems above, wet snow slides are possible on slopes above the valley floor—especially if rain is falling.

Avalanche Discussion

Above-average snowfall, arctic cold, extreme winds, and spring-like conditions—and it's not even January. What will this winter bring next? A wet and wild atmospheric river event anyone? Today's avalanche conditions will be closely tied to the weather forecast, and we all know how fickle those can be. They are doubly so when warm temperatures, fluctuating snow lines, and rain are in the mix. Today brings to mind the age-old adage: Weird weather produces weird avalanches. 

Rewind to yesterday. Persistent weak layers remained a concern throughout our forecast area. In fact, riders in the 4th of July drainage of the White Clouds remotely triggered a large avalanche from flatter terrain an estimated 1/4 mile away. This appears to have failed on sugary, faceted snow buried in late November. In addition to this weak layer, we have others closer to the surface. So the avalanche picture wasn't exactly rosy—and that was yesterday. Back to the present, today's storm is forecast to add 1-2" of snow water equivalent (10-20+" of snowfall) to an already marginal snowpack. Strong to extreme winds, very warm temperatures, and a rain/snow mix at lower to middle elevations—these only make things worse.

Today's avalanche conditions are only complex if you try to predict what type of avalanche will occur. Will it be a monster, 3-5' thick persistent slab that slams a pile of trees on the valley floor? Will it be a somewhat smaller, 1-3' thick persistent slab that breaks on one of our newer weak layers? Or how about a slab of moist snow that oozes down a steep slope above the valley floor? Who knows—I can't say that I do with a high degree of confidence. But I do know that avalanche conditions will be western out there today. When the going gets complicated, the best approach is to simplify: avalanches of some variety are very likely today, and they have the potential to be very destructive and to reach the valley floor. When conditions like this exist, the travel advice is also simple: avoid traveling on or beneath slopes steeper than 30 degrees, including valley bottom runout zones.

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