Avalanche forecast

Southern Wallowas

Wallowa Avalanche Center
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Avalanche danger

Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

New snow and wind have built wind slabs on northwest through east-facing slopes.  Avoid slopes with cornices, wind pillows, and textured or smooth hollow hollow-sounding snow. Slopes that have not been affected by the wind may contain storm slabs, use caution on any slope steeper than 30 degrees.

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

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    The 12-18" 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.

    (2/16/2024) Minor cracking under skis and small windslabs on exposed NW facing terrain.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    The Southern Wallowas above 5500'  have received 1.5-2" of water and 16-20" of new snow Since Thursday. This new storm snow fell onto existing variable snow surfaces. These old snow surfaces include slick melt-freeze crusts on southern exposures and potentially surface hoar on more protected slopes at and below treeline. Surface Hoar was widespread before this storm and there is uncertainty about whether it was buried intact and is reactive.

    An additional consideration is the possibility of triggering loose dry avalanches on steep slopes ( >35 degrees) where the new snow lacks the cohesiveness to produce a slab avalanche. 

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. 

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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