Lawinenlagebericht

Rattlesnake

West Central Montana 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 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Triggering a persistent slab avalanche in areas of previous wind loading is possible today. Deeper persistent slab avalanches up to 5 feet deep are unlikely but possible at upper elevation north aspects. Wet avalanches are possible at low elevations. 

If you see cracking or find weak snow with a slab above, avoid slopes over 35 degrees. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–3

    Old wind slab sitting on top of near surface facets has made it possible to trigger a persistent slab up to 2 feet deep along ridgelines. 

    Triggering an avalanche up to 5 feet deep remains possible on north aspects at the upper elevation. While unlikely, the consequences of an avalanche this size are potentially deadly. 

    Avalanches are likely to fail on depth hoar and mid pack facets with a slab above. 

    Terrain management is the only way to avoid this problem. If you find faceted snow underneath a slab, stick to slopes below 35 degrees. Avoid convex rollovers or shallow areas of the slab, as these are likely trigger points.

  • Loose Wet

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

    Warm temperatures today combined with above freezing temperatures last night will lead to low elevation wet loose avalanches today. These may be found in the mid elevation today as well, especially if winds remain light or southern aspects see periods of direct sun.

    If you see rollerballs or the snow becomes wet and unsupportable, stay off of slopes over 30 degrees and do not travel under avalanche paths. 

Avalanche Discussion

Weather the past two days has been a combination of warm temperatures, light wind, and rain to mid elevation. Upper elevations received only an inch or two of dense snow. 

Yesterday, we did not see significant wet snow avalanche activity despite warm temperatures. In many areas, there was just enough wind to keep the snow cold. Last night did not have a solid re freeze, and with warm temperatures forecasted today, low elevation wet loose activity is likely. If you see rollerballs or the snow becomes unsupportable, stay off of slopes over 30 degrees and do not travel under avalanche paths. 

Across all zones, the persistent slab danger for a full depth avalanche is improving, but the potential remains. Layers of rounding facets, depth hoar, and crust/facet combinations still show high propagation potential when triggered. You are more likely to affect these weak layers at shallower parts of the slab or on convex rollovers. It is becoming increasingly unlikely to trigger an avalanche on the deeper layers, but the consequences remain high. The buried surface hoar layer from Thanksgiving has mostly disappeared and is no longer a primary concern. In areas with a thick Christmas crust, affecting the deep weak layers is unlikely. 

In the upper snowpack, there is a new buried persistent weak layer at upper elevations and along ridgelines. The wind slab formed Monday and Tuesday sits on top of buried near surface facets. In the Seeley Lake zone, this slab is also sitting on top of surface hoar and has produced multiple avalanches. 

Take the time to dig in the snow and if you find a slab on top of weak snow, stay off slopes over 35 degrees. If you see cracking or experience whumfing in areas of old wind slabs, avoid slopes over 35 degrees. 

Check out this blog post on the state of our snowpack. We will try to update with a new blog post once a week. If there is a topic you are interested in learning more about or have an idea for a blog topic, send us a message. If you are considering taking an avalanche course this winter, find one near you on the courses tab on the home page. 

Let us know what you are seeing out there by submitting an observation.

Ski and ride safe! 

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