Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

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

Kernpunkte

Up to 2 feet of new snow has fallen in 48 hours. Natural and human-triggered avalanches are expected.  Keep your powder fever in check today by evaluating steep slopes, especially if you see wind-drifted snow or shooting cracks around your skis or machine.

 

 

Lawinenprobleme

  • Wind Slabs

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

    Increasing westerly winds will easily transport the recent low-density snowfall throughout the day. Slabs may form on top of weaker snow, adding to their instability. The slabs will increase in thickness and size as you gain elevation.

    Look for blowing snow as a sign that fresh slabs are forming. Scoured or textured surfaces indicate the wind has been at work. Dense, stiff snow is a clue you have found a slab. Cracking or collapsing directs you to seek out lower-angle terrain.

     

    (2/24/2023)

    A soft slab avalanche on a cross-loaded convexity. This is also known as a wind slab.

    Photo: mark dundas

  • Storm Slabs

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

    Substantial low-density snow fell in most mountainous areas over the past 48 hours. This snow rests on soft snow from the past few days above a crust. On some slopes, the snow above the crust is faceted and may allow you to trigger slides remotely. These slides could propagate wider and higher above you than expected.

    Search for and avoid relatively stiff, cohesive snow. This will be where your skis, boards, or machine do not sink as deeply into the new snow. Cracking in this snow indicates an unstable slab and directs you to seek out lower-angle terrain.

    (1/7/2024)

    Storm Slab in the Swan.

    Photo: Kaleb Retz

Avalanche Discussion

“Top 5 deepest days in the Flathead.” “We were SO pleasantly surprised.” “Super terrific S2 storm snow.” “The storm finally delivers!”  These were descriptions captured from observations on Sunday. 

The storm favored the Whitefish, the Swan, and the Flathead Ranges, where more than an inch of water fell. Due to the cool temperatures, the storm snow fell more like cold smoke or champagne powder than we usually see in Northwest Montana. Due to the low density, snowfall totals are difficult to capture accurately, but observers report 1-2 feet or more. The snow density was less than 10% in most locations and probably closer to 5%. This is a welcomed contrast from the last two weeks of mostly dry, inversion-dominated weather. 

Natural and human-triggered storm slabs and loose dry avalanches were reported from various aspects and elevations (Observation 1, Observation 2, Observation 3). Today, we expect a temporary break in the active storm pattern, with increasing southwesterly winds anticipated to transport the low-density snow. Given that much of our region has a variety of crusts now buried under the new storm snow, a building wind slab problem will likely be found on east-north-west aspects.

In some sheltered locations, you may encounter sluffing. Remember that if you venture into steep slopes, even a small slide may be consequential if this sluff catches you off guard and pushes you into trees, rocks, cliffs, or other hard objects. Low elevation hazards are still plentiful, as our snowpack remains thin below 6000 feet in many locations.

 

 

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