Lawinenlagebericht

Banner Summit

Sawtooth Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 2 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Be on the lookout for drifts and slabs of wind-blown snow that grow in size, distribution, and sensitivity throughout the day. Cracking in the new snow is a clear sign of instability. Triggering much larger avalanches on weak layers in the upper few feet of the snowpack is much less likely, but the consequences would be grave. These larger slides are most likely in steep, rocky terrain where the wind has sculpted the snowpack and the weak layers are easier to impact with your weight.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    Today's storm brings 3-5 inches of snow to upper elevations and rain to the valley bottom. Moderate winds blowing out of the SW accompany this precipitation. Wind slabs will gradually build throughout the day. While these slabs will be relatively small and isolated, they may be reactive to your weight thanks to the rate at which they form. Look for these slabs near ridgelines and mid-slope gullies in wind-exposed terrain. Cracks shooting out from your skis or machine are a clear sign that the new snow you are moving through is unstable. 

    Even small slabs can knock you off your feet or your machine. Consider the consequences of getting tossed downhill in the terrain you are traveling through. 

  • Persistent Slabs

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

    Weak layers buried under dense slabs in the upper few feet of the snowpack have had some time to rest and are trending towards unreactive. However, the consequences of triggering one of these beasts would be severe. If you dig down, you'll find facets and bands of surface hoar on shaded slopes and icy crusts with associated facets on slopes that face the sun. Slides are more likely on shaded slopes, but sunny slopes remain suspect as well.

    Your first sign of instability involving these weak layers would be the large avalanche you trigger. These slides may break well above you on the slope and fail widely. You can trigger slides like this from a distance away from the slope that avalanches (remote triggering). You can significantly reduce your risk of encountering a slide like this by steering clear of steep, rocky, heavily wind-affected terrain. 

    (3/14/2024) This large avalanche was triggered on ascent as three people booted up the final 20' to the saddle at the top. No one was caught. The avalanche broke 2-4+ feet deep on faceted snow. Sawtooth Mtns, N @ 9,900'.

Avalanche Discussion

Yesterday saw the end of a 10-day string of hot temperatures and sunshine. Our snowpack did a lot of melting and settling during this period (10-day temperature chart in the Media Gallery below). Many lower and middle elevation slopes lost water out of the bottom of the snowpack and creek gauges showed a spike in discharge. Thick, icy crusts formed at the snow surface on all slopes that face the sun, while shaded slopes at middle and upper elevations remained dry and crust-free.

A storm pushes into our area this morning. Precipitation will come in brief but intense bands and will be accompanied by moderate, gusty winds blowing out of the SW. Today's snow arrives at warm temperatures which cool as the day progresses. New snow is falling on a variety of surfaces, most of which look like they will provide a decent interface for the new snow to bond to. The most concerning surfaces that we've seen are on shaded middle and upper elevation slopes where slick, wind-polished surfaces have undergone some faceting. Today's storm will not significantly increase the avalanche hazard. Without much snow for ammunition, today's slabs will be isolated and relatively small. Pay attention to how much new snow you are moving through and consider the consequences of getting tossed downhill in the terrain you are in. 

Beneath the new snow, a variety of weak layers exist in the upper few feet of the snowpack. The character and sensitivity of these layers varies from slope to slope. We observed some wet slabs failing on these layers during the major warm-up,  but the most recently triggered dry slab avalanche failed in the Sawtooths on March 14th (photo here). The likelihood of triggering a slide involving these layers has decreased significantly, but hasn't gone away. You'd be most likely to trigger an avalanche involving these layers on very steep slopes in alpine terrain. Here, the snowpack is variably thick, allowing for better access to these weak layers. Avalanches that fail on these layers would be difficult to escape unscathed.

It is spring, and valley bottom locations will see highs in the mid 40s F and sprinkles of rain and sleet today. The snowpack at lower elevations has experienced many cycles of melt and freeze and these warm temperatures and rain are unlikely to produce widespread wet snow issues. As always, if you are finding a wet pile of snow on the slope you are playing on its worth considering the possibility of starting small wet snow avalanches. 

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