Lawinenlagebericht

Central Cascades

Central Oregon Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Nope the "avalanche forecast machine" isn't just stuck on considerable.  Despite variations in the weather, the avalanche danger has remained constant.  Moderate and Strong winds have continued to blow snow onto lee slopes (those that face away from the wind) and Wind Slab avalanches remain likely.  Avalanches triggered in wind blown snow could be large.  Up to a foot and a half of new snow below treeline on open slopes and glades means that there remains a possibility of avalanches even in lower elevation terrain.  These avalanches will mostly be smaller but could be large if they involve particularly weak snow on north slopes.

Lawinenprobleme

  • Wind Slabs

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

    Areas near the crest have received about a foot and half of new snow in this latest storm.  We have had continuous winds from the west at varying speeds.  Today I observed moderate snow transport near Moon mountain.  This means that Wind Slab avalanches will continue to be likely on north, south, and particularly east slopes at higher elevations and in open terrain.  Wind Slab avalanches could be large enough to bury or injure a rider.  The forecast calls for a wind shift to more southwest and Strong speeds on Wednesday.  Continue to use cautious routefinding and conservative terrain choice if traveling on the indicated slopes.

  • Storm Slabs

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

    In open terrain I observed that Monday night's snow had a bit more cohesion than the very low density snow that fell on Monday.  Storm Slab avalanches were possible on Monday.  Storm Slabs typically settle quickly, but Wednesday could be a bit too soon to put this in the rearview.  Observations on test slopes (very small steep slopes) and in the skin track have been key during this storm to sort out how cohesive the surface snow is, and whether Storm Slabs or Dry Loose avalanches are possible.  On Wednesday, look for settlement cones (cracks in the snow that's mounded around trees) as an indicator that the new snow may be settling.  Work into steeper angles gradually.

    The one exception to this pattern is where our latest snow has fallen on buried surface hoar.  On these slopes avalanches could propogate far and be large.  Surface hoar has only be observed in isolated locations.  It is most likely on sheltered, north facing slopes, so it's a good idea to a little digging in the snowpack if you are touring on north slopes.  This layer is likely 40-55 cm below the surface in sheltered terrain.

Avalanche Discussion

The weather has been cold and snowy!  Wednesday will be a bit of a break, but we won't have a break in the considerable hazard, as the next round of heavy snowfall should begin late Wednesday night or early Thursday morning.  The majority of instabilities have existed within the new storm snow.  The one exception is a very sparse layer of buried surface hoar that is now buried 40-55 cm. at the interface of the storm snow and older snow.

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