Bollettino valanghe

Elkhorns

Wallowa Avalanche Center
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Pericolo valanghe

Sat
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

You can trigger an avalanche large enough to injury, bury, or kill you on wind-loaded slopes that are steeper than 30 degrees.  Recent avalanches, blowing snow, or cracking of the upper snowpack are all clear signs that wind-loaded slopes are primed to avalanche.  Seek out lower-angle slopes in wind-sheltered terrain if you see signs of instability.   

This Forecast is Sponsored by Quickhatch Provisions in Joseph, OR.  

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2.5

    Today's storm system will bring additional snow and wind to build another round of wind slabs to mid and upper elevations.  Expect to see avalanche danger increase as the day progresses.  The Elkhorns and Southern Wallowas are forecasted to receive an additional 8-10" of snow with moderate to strong winds. 

    All the signs were very clear yesterday as observers found natural avalanches, cornices, skin tracks that filled in rapidly, and cracking in wind-stiffened snow in exposed terrain.  Wind slabs that formed yesterday will still be sensitive today, but they may be covered with new snow or fresh wind slabs and be more difficult to identify.   If you ride your machine or ski across stiffened snow and stay on top of the snow, you have likely found a wind slab.  

    Avoid terrain that is or has been loaded with wind-blown snow.  Keep an eye on mid-slope features lower down from ridgelines that could be cross-loaded and be primed to catch you off guard.  Where possible, utilize small but steep test slopes to test the reactivity of newer or older windslabs. (think no taller than a single-story house with no terrain trap below).   

    (12/26/2024) Textured Snow and shooting cracks are clear signs of unstable and wind loaded slopes.  

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    In lower elevations where we will see less wind, storm slabs will be possible today especially during or right after times of higher-intensity snowfall rates.  Yesterday, observers found reactive storm slabs on small test slopes.  As you are skinning or riding your machine, try to step or ride above the existing track to see if you can get cohesive blocks of snow to slide off.  Stop and isolate small columns with your hand or ski pole and pull on the back of the column.  Is it sliding easily as a cohesive block on an old snow surface?  If it is,  you've got all the right ingredients for a slab avalanche and should stick to terrain less than 30 degrees that doesn't have any terrain traps, where the consequences of even a small avalanche could be magnified.  

    A 6-8"  cohesive slab breaking on a steep rollover.  This was found in a valley bottom that was void of any wind-blown snow. 

Avalanche Discussion

What is it? Our headline story for this holiday week is significant snowfall accompanied by strong winds out of the South/Southwest.  Most avalanches occur during and just after times of intense loading events.  We get the double whammy of loading with this series of storms:  Loading through rapid snowfall rates in combination with wind loading of snow onto leeward slopes.  

Where is it? You will be able to find unstable snow in many locations today.  Today is not the day to toe the line.   If you do decide to travel near or in avalanche terrain, wide terrain margins will be essential.  You can most likely trigger a large avalanche on wind-loaded slopes steeper than 30 degrees.  You will most likely encounter wind-loaded slopes at mid and upper elevations, on most all aspects.    In wind-sheltered areas- if you find new storm snow in the 6-8" depth range, you could potentially trigger a storm slab avalanche.  Additionally, if you find yourself below the snow line (about 4500')  look for signs of wet loose avalanches.  

What to do about it?  If you head out into the hills, I would suggest having a conservative mindset, avoid potential avalanche paths that may be above or adjacent to your intended route, and testing the reactivity of new snow by utilizing small and inconsequential test slopes.  If you see a cohesive slab of snow break at your machine or boards, you can bet that triggering an avalanche on a larger slope is likely.  

What's going on a bit deeper?   While we are mainly worried about storm slab and wind slab avalanches, There is still the potential to trigger a deeper avalanche into older snow.  While we have a mostly right-side-up snowpack below the new snow, there are still some layers that we are keeping an eye on.  Yesterday, I found reactive and propagating results from three different layers within the upper 2 feet of the snowpack.  (See a recent observation here)  These reactive interfaces were mostly below the most recent storm's snow and have the potential to be triggered from a  smaller wind slab avalanche.  We call this "stepping down".   

We have also been tracking a weak layer that was formed during high pressure around Thanksgiving.  The Thanksgiving Drought Layer (TDL) is a layer of rounding facets (healing sugar snow) that can be found 3-4 feet from the surface.  We have been conducting numerous stability tests to assess the reactiveness of the TDL, and we have not been seeing as reactive results as we were a week ago.  This is a nice trend to see, but I am still weary of this layer.   Suspect areas that may harbor this unstable layer are mid and upper elevations, on the northern half of the compass, and in thin snowpack depths.   You can read some recent observations that target this layer here. 

If you get out into the backcountry today, help us reduce uncertainty by letting us know what you are seeing.  Submit an observation here.  

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