Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

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

Kernpunkte

Dangerous avalanche conditions still exist due to continued warm temperatures. Reports of very large natural avalanches are still being documented, proving the cycle is not quite over.  Give steep terrain plenty of room if taking advantage of the sunshine today.

Lawinenprobleme

  • Persistent Slabs

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

    Shaded areas above 6500 feet will be the last slopes to feel the impacts of the warm temperatures. The problem child is a layer of weak snow buried around a crust roughly 2-4 feet down.  If found, choose your terrain carefully.  Areas on the slope where the slab thins out are places where you could trigger a large Persistent Slab avalanche.  Travel around convexities and off of slopes connected to places where you find this combination.

    Dry snow may still be found on upper-elevation slopes that are shaded from the sun.  This photo is of a natural avalanche that failed a few days ago. The green line indicates the length of the crown. 

  • Wet Slabs

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

    A natural avalanche cycle of Wet Slab avalanches continues.  Upper and middle elevations are living in above-freezing conditions. Meltwater has made its way to a weak layer buried 2-4 feet below the surface, causing it to become unstable. Steep slopes getting hit by the warm sun will be the most likely to avalanche. The weight of a skier or machine has the potential to tip the scale and cause a large and deadly avalanche.  Avoid steep slopes and give the runouts a wide margin because wet debris can travel surprisingly far distances.  Wet Slab avalanches are destructive and will fail without warning.

    Rocky terrain being hit by the sun will be the most common area for wet snow avalanches. 

Avalanche Discussion

“Hazardous,” “scary,” “difficult,” and “ ... the worst” were all descriptors from people who traveled into the mountains yesterday (January 30th).  The unseasonably warm temperatures have caused significant changes to our snowpack and ease of travel.  A report from John F. Stevens Canyon describes knee-deep post-holing in isothermal snow. Meanwhile, I was in Noisey Basin on a very supportable and thick crust. 

The Flathead Range and Glacier National Park appear to have seen the most action with very large (destructive size 3) avalanches over the past 3 days.  Observers reported moist snow above a facet/crust combo that still lingers from late December.  These ranges seem to be warmer with a shallower and weaker snowpack.  Combine all of those to get a resulting widespread cycle of persistent and wet slab avalanches.  Many of these have run long distances and entrained nearly the entire season’s worth of (dismal) snow.  

For those of you brave enough to venture into the challenging conditions today, remember what is above you.  Upper elevation temperatures have been above freezing for several days, and the snowpack continues to be prime for wet snow avalanches.  Keep time spent under big terrain to a minimum.  Travel patterns that you are used to may take much longer than anticipated, or not be possible.  

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