Lawinenlagebericht

Bitterroot

West Central Montana Avalanche Center
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Lawinengefahr

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

Kernpunkte

Natural wet loose avalanches will be likely today in areas of direct sun. If you see small point releases beginning to fan out or entrain more snow, it indicates that the wet loose cycle has started for the day and that it is time to get out of avalanche terrain and move to nonsolar slopes. 

Triggering a larger persistent slab avalanche is unlikely, but specific pockets of weak snow remain in rocky terrain and on convex rollovers. You are unlikely to see any red flags before the avalanche fails unless you dig in the snow to look for weak sugary snow with a slab above. 

If wind and high cloud cover show up today and keep the snow from getting wet, avalanche danger will be low. 

Lawinenprobleme

  • Loose Wet

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

    Expect to see natural and human triggered wet loose avalanches if the sun stays out for an extended period today. Avalanche size will be dictated by the size of the slope and how much wet snow can be entrained in the avalanche as it runs. Larger slopes will be capable of producing avalanches up to D2 in size. The timing of the wet, loose snow will depend on how stout the melt-freeze crust is at the surface. Areas with a thicker crust will take longer to break down, whereas areas with a thin crust at the surface or no crust will become wet faster.

    There is some uncertainty on the likely versus possible for this problem due to the higher than expected windspeeds and increasing high cloud cover, which could help keep the snowpack cool in wind-exposed or upper-elevation terrain.

    If you see a widespread rollerball cycle, or small point releases beginning to fan out and entrain more snow, it is time to move out of avalanche terrain, be aware what is above you, and move to non solar slopes. 

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–3

    Triggering a larger persistent slab avalanche that fails 3-5 feet deep has become unlikely. Specific pockets of poor snowpack structure remain with buried January facets, and facet crust combinations.

    This problem still lingers in areas with rocky convex rollovers, however, even in these areas snowpit tests have become increasingly unreactive. You are unlikely to see any red flags like shooting cracks, whumphs, or feel collapsing before an avalanche occurs. 

    The trouble with looking for this problem is that you must expose yourself to the terrain most likely to produce an avalanche to dig and look for it. Digging above or adjacent to rocky rollovers will likely show a different snowpack structure than what can be found directly in the rocky rollover. If you dig in a safe area and identify weak, sugary snow with a slab above, the best bet is to stick to lower angle slopes less than 35 degrees. 

Avalanche Discussion

Only a trace of new snow has fallen since last weekend’s forecast with temperatures climbing to just above freezing each day at most weather stations. This weekend, expect the spring weather to continue with partly cloudy skies and temperatures climbing to near 40. A moderate to strong west wind will impact upper elevation and exposed terrain today, which could help keep temperatures cooler.

With the spring weather comes the usual list of spring snowpack problems. Expect wet loose avalanches today, but things will not warm up enough this weekend to produce large wet slab avalanches. 

We are beginning to see some glide cracks open. Glide avalanches are the most difficult to forecast or understand due to their unpredictability. The time between a crack opening up and the avalanche can vary from minutes to months. You are unlikely to trigger a glide avalanche as a person, but natural avalanches are possible. Avoidance is the answer. If you see open glide cracks, do not travel underneath them. 

A week of sun and warm weather has helped melt overhanging cornices back to vertical. Much of the natural cornice failure cycle has passed. If you see an overhanging cornice in direct sun or a period of warm weather, do not travel or hang out underneath it. 

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Ski and ride safe.

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