Lawinenlagebericht

Elkhorns

Wallowa Avalanche Center
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Lawinengefahr

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

New snow and wind have built wind slabs on northwest through east-facing slopes.  It remains possible to trigger a deeper and more destructive avalanche failing on persistent weak layers buried 2-6' deep in the snowpack.  To avoid avalanches, steer clear of terrain steeper than 30 degrees, wind-loaded slopes, and areas that harbor a shallow snowpack (less than 3 feet).  

This forecast is sponsored by La Grande Sno-Drifters Snowmobile Club.

Lawinenprobleme

  • Wind Slabs

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

    The 6-8" of snow that fell on Thursday and Friday has been easily transported by SW winds and deposited on NW-E facing terrain at and below ridgelines. Moderate southeast winds on Saturday continued to move snow building larger wind slabs. The snow that arrived last night was accompanied by more moderate wind adding to the already existing wind slabs.

    Look for and avoid slopes with cornices, wind pillows, textured snow, and smooth hollow sounding snow. Cracking in the new snow is a sign you've found a wind slab.

    (1/13/2024) Photo: Caleb Merrill

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2.5

    The snowpacks in the Northern Wallowas and Northern Elkhorns are currently weaker than the other forecast zones. Despite the warm weather and rain in late January, poor snowpack structure still exists. The possibility of triggering a persistent slab avalanche is still a very real one. The slab of snow sitting above the weak layers has continued to gain cohesion over the last couple of weeks.  This means that if you were to trigger a persistent slab avalanche, it would propagate further and be larger than you might think. Triggering one of these avalanches would have serious consequences.

Avalanche Discussion

Snow on Thursday and Friday fell on a variable and weak old snow surface.  After a brief break in the snowfall action Saturday, snow picked back up overnight.  Winds from the SW-S-SE picked up Saturday and continued Saturday night.  These winds built wind slabs on NW through E facing slopes.  Where storm totals are around 6" or less, or the new snow remains uncohesive, the main problem will be loose dry avalanches on slopes > 35 degrees. These small avalanches may not bury you, but they could inflict significant bodily harm if they were to take you off your feet or sled and sweep you into obstacles like rocks and trees. Where storm totals exceed 12"  and there is no wind effect there may be a storm slab problem. The best practice for avoiding these problems is to stick to slopes < 30 degrees (i.e. stay out of avalanche terrain). 

There was widespread surface hoar formation before the Thursday- Friday storm arrived. Surface hoar is a notorious weak layer when buried. There is uncertainty about whether this surface hoar was buried intact and is reactive.  Pro Observer Sarah Jakober went searching for surface hoar in the Elkhorns and did not find it.  Yesterday in the Southern Wallowas we found it buried intact but laid over and unreactive in stability tests. Another observation from the Western Wallowas mentions finding it yesterday.  Likely locations for encountering buried surface hoar include more sheltered and protected slopes at and below treeline. If you are hearing the snowpack whumpf underneath you or seeing shooting cracks propagate outwards as you travel, then surface hoar is likely present at the old/new interface. This should have you dialing back your terrain choices and keeping off and out from under slopes > 30 degrees. 

The persistent slab problem continues to plague our northern zone. There are weak layers toward the bottom of the snowpack that remain reactive. Check out WAC forecaster, Caleb Merrill's observation from Mt. Howard a few days ago.  Recreationists should continue to be vigilant and seek out critical snowpack information to assess the reactivity of these deeply buried weak layers. The consequences of triggering an avalanche on these weak layers would be severe. 

Recent observations in the Elkhorns, Southern Wallowas, and Northern Wallowas paint a great picture of what this storm has left behind. 

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