Avalanche forecast

Northern Wallowas

Wallowa Avalanche Center
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Avalanche danger

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

Human-triggered avalanches remain likely, where the wind has formed a slab above weak snow that is now buried 1-2' below the surface.  You can find this dangerous combination anywhere the wind has stiffened the surface snow to create stronger snow sitting on top of weak snow from last week's cold snap.  To avoid triggering a large avalanche avoid riding slopes >35 degrees, don't hang out in run-out zones, and use conservative terrain selection.  

Today's forecast is sponsored by Terminal Gravity Brewing in Enterprise, OR.  

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    The What: Last week's cold snap produced two persistent weak layers, that are now buried 1-2' below the snow surface.  Weak facets and surface hoar were observed yesterday in two snowpits, one at 8,000' (West Aspect) and the second a 6,000' (West Aspect).   In locations where a more cohesive slab has formed above these weak snow grains, we've seen numerous human-triggered avalanches this week.  They have been on a variety of aspects above 7,000'.  All of these slides have been remote triggered from low-angle terrain!

    The Where: You can find weak snow on nearly all elevations and aspects buried below the storm that rolled through last Sunday, which produced 1-2' of snow.  Last weeks frigid temperatures created weak snow at the surface which we call near-surface facets, and surface hoar.  This weak snow has been reactive in areas where a slab has formed above it.  

    What to do: Surface hoar and facets don't disappear overnight, that's why we call them a persistent weak layer.  You may feel whumping or collapsing or observe shooting cracks, but not always.  If you truly want to know what's beneath you, get out your shovel and do some digging.  If you find strong snow, over weak snow you have a slab.  Stick to lower-angle terrain, increase your margins, and ski and ride one at a time in steep terrain.  

    So What: Yesterday while out riding in the East Fork of the Pine, I observed snowmobile tracks on steep slopes, with numerous trigger points.  So how come these folks didn't trigger an avalanche, and why should I take your advice you might ask?  The reality is, the snowpack is incredibly forgiving, most of the time, even when the snowpack structure is poor.  But, when the structure is poor, I reduce my personal risk threshold, because all I have to do is find the sweet spot, and that might make the difference in whether I get to come home safe at the end of the day.  

     

    (2/9/2023)

    Photo of a remotely triggered persistent slab avalanche in the Southern Wallowas. This avalanche occurred on a northeast-facing slope at 7850'.  Avalanche occurred on Thursday.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    The winds have backed off in the last 24 hours, but there still remains the possibility of triggering a more stubborn wind slab near and above the treeline.  Look for clues such as cracking, strong over weak snow, and surface texture for clues of windslab formation.  Triggering a windslab 1-2' deep is not out of the question on steep slopes >35 degrees today.  

    (2/9/2023)

    This photo was taken Wednesday in the Southern Wallowas. Elevation around 8000' on a southwest aspect. The reported crown depth was 1'-2'. The slab consisted of wind-transported snow. The weak layer was reported to be buried surface hoar or facets.

Avalanche Discussion

One more thing to keep in mind today, temperatures could warm to above freezing on some south-west facing terrain. Sunshine and warm temperatures can dramatically weaken newly fallen snow making it easier to trigger avalanches on steep solar aspects. If we are seeing roller balls on the snow surface, signs of snow melting off of tree limbs (snow bombs), and observing other signs that the snow is melting and therefore weakening, we need to exit these steep south-west facing slopes and head for shady north facing slopes to avoid triggering a loose wet avalanche. Also, fresh cornices exposed to a lot of sunshine and warmer temperatures could be affected and weakened by the sun as well today. If we find ourselves traveling on corniced ridgelines today, we need to stay well back and away from the edge of the cornices. Cornices tend to break further back from the edge than we might expect.

Thanks to all that posted the great photos and observations the last few days!

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