Lawinenlagebericht

Gunnison

Crested Butte Avalanche Center
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Lawinengefahr

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

Kernpunkte

The chances of triggering a slab avalanche continue to decrease slowly, but the consequences remain severe if you do.  The problem generally exists on the north half of the compass, and it may require you to find a thin spot in the slab to release.  Thin spots or trigger points are not always identifiable at the snow surface.  You can reduce the likelihood of avalanche by avoiding slopes with variable depth due to previous winds and rocky areas or by choosing lower-angled terrain.  You can reduce the consequences of an avalanche by selecting small slopes without terrain traps.  Increasing cloud cover and a cold front greatly reduce the threat of wet avalanche activity.

Lawinenprobleme

  • Persistent Slabs

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

    Weak facets, depth hoar, or collapsible crusts exist on the northern half of the compass and on some sunnier aspects at high elevations.  Slabs on top of these weak layers average 1.5 to 3 feet thick in wind-sheltered terrain. Slabs are thicker and harder in wind-drifted terrain and can step down through older slabs to the ground.    This problem has become stubborn to triggers, often requiring a thin spot on the slope, such as near buried rocks, trees, or where slabs thin from wind effects. Avalanches can break widely across multiple terrain features and be remotely triggered from flat terrain near or below steep slopes without warning signs. The problem can be avoided on slope angles consistently less than about 30 degrees.  

    A couple of persistent slab avalanches that were remotely triggered in the upper Cement Creek area on Friday. 

Avalanche Discussion

Increasing cloud cover and cooler temperatures significantly reduce the threat of wet avalanche activity today.  A reasonable refreeze overnight, thanks to a period of mostly clear skies, likely prevents wet issues from redeveloping as the clouds and colder air arrive midday.  Watch for a wet, mushy snowpack if clouds and colder air arrive later than forecasted.  Head for a colder snowpack or lower-angled terrain if you find a saturated and punchy snowpack.

The persistent slab problem is the primary issue you need to manage.  Avalanche activity and signs of instability have slowed since the snowfall and wind loading ended about 10 days ago.  Even with this decline, human-triggered avalanches remain a threat on some slopes highlighted by the Persistent Slab distribution rose.  Snowmobilers remotely triggered a pair of Persistent Slabs from flat terrain on Friday, 2/28, near Star Pass.  Another observer noted collapsing in the valley bottom of Cement Creek on Saturday.  Poor snowpack structure is fairly easy to find on northerly facing slopes and some upper elevation east and west slopes; however, without recent loading, releasing a slab has become less likely, but the consequences remain dangerous.  You may need to find a trigger point, where slabs become thinner to release a large slab, but identifying these trigger points can be challenging or impossible.  Some slopes look obviously thin or very rocky and should be avoided.  Some slopes look uniform in depth but could be masking trigger points below the surface, leaving a landmine for you to cross.  This video from Bruce Jamieson gives a nice overview of trigger points and demonstrates how trigger points can be difficult to see at the surface.  

An incoming storm may change avalanche conditions on Tuesday. Snowfall begins mid-Monday and lasts through Tuesday. Snow and wind may cause a new avalanche problem. .

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