Avalanche forecast

Elkhorns

Wallowa Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Sunshine and warming temperatures will increase the chances of triggering a wet loose avalanche on steep slopes.   Avoid steeper slopes as the snow is becoming wet and heavy.   Isolated pockets of wind-drifted snow may remain reactive just below corniced ridgelines above the treeline.  

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Avalanche problems

  • Loose Wet

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

    Wet loose avalanches within last week's storm snow should be your main concern today.  A thin melt-freeze crust on the surface will likely be found on all but due northern aspects this morning.  It will warm and soften throughout the day.  By mid-day start to look for natural roller balls and small wet loose avalanches around rock bands on aspects that the sun is directly affecting.  Once this occurs, you may be able to trigger wet cohesionless snow in the upper snowpack. 

    While these wet loose avalanches are expected to remain small today, getting caught up in one can push you off your feet and carry you over consequential terrain or push you into a terrain trap such as a creek bed or gully.  As the snow becomes wet and heavy under your skis or machine, move to lower-angle terrain or shadier aspects.

    D1 Wet Loose Avalanche on East aspect

    Photo: Caleb Merrill

  • Wind Slabs

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

    By and large, wind slabs have relaxed and become less reactive than earlier in the week.  However, there could remain some lingering pockets of sensitive wind-drifted snow along upper elevation ridgelines on NW through North through NE aspects. 

    On Wednesday moderate to strong winds from the Southeast, South, and Southwest transported storm snow onto leeward aspects along ridgelines and exposed terrain.  As the winds backed off, snowfall continued and buried these wind slabs, making clues of wind loading a bit less obvious.   Be suspicious of steep slopes near ridgelines on the north half of the compass, especially where they sit below corniced ridgelines.  

    On Thursday, Observers in the Western Wallowas and Elkhorns found 2-5" of new snow covering 8" thick wind slabs on terrain exposed to the wind.  Collapsing and whumphing was noted and was caused by wind-stiffened snow failing just above the melt-freeze crust found about 18" from the surface.  Propagating results in Extended Column Tests were also noted at this layer. 

    In the Northern Wallowas on Thursday, several small natural wind slabs were noted running a couple hundred of feet and breaking about 6" deep just below corniced ridgelines.  

    Look for signs of wind-stiffened snow in your travels today such as cracking around your skis or machine and rippled, pillow-like features.  Find small unconsequential test slopes to ride or walk across to test the sensitivity of wind slabs.  Avoid areas that are wind-loaded in terrain greater than 30 degrees.  

    (3/28/2024)

    D1 natural windslab released below Wing Ridge from Wednesday's wind and snow event. 

    Photo: Wallowa Avalanche Center

Avalanche Discussion

In addition to the avalanche problems mentioned above, Dry Loose avalanches were easily triggered in terrain steeper than 35 degrees on due north aspects yesterday.  They were very manageable and predictable, but could certainly knock you off your feet if you were not expecting them.  Keep your head on a swivel if riding in steeper terrain and are finding cold dry snow on sheltered upper elevation Northerly aspects.  They will become less likely as temperatures climb throughout the weekend, but keep them in mind if riding above consequential terrain. 

The 1-2 feet of new snow that has fallen since Monday sits above a supportive melt-freeze crust from the mid-month warmup that was buried on 3/22.  Observers are finding this crust to be of varying thickness from 1" to 6" depending on the aspect and elevation.  Some weaker snow has been found around this crust, and we will be keeping an eye on this.  Continue to monitor the new snow and its interaction with the 3/22 melt-freeze crust.  Dig down to the crust and see if the new snow is consolidating into more of a cohesive slab.   If you can hold the new snow between your hands and take a bite out of it like a big ol cheeseburger, you've got a slab.  Step above the skin track and push the new snow downhill to see if it is sliding easily onto your skin track. You can also gain a lot of information about the reactivity of these stiffening slabs by riding across small test slopes that have little to no consequence.  Observers in the Western Wallowas and Elkhorns have found 4-finger hard slabs propagating in Extended Column Tests.  They are failing just above the 3/22 crust.  Check out recent observations from the Elkhorns from the last few days here and here. 

 

Persistent weak layers: The Needle in the Haystack

While becoming increasingly unlikely, the off-chance of triggering a deeper and more destructive avalanche failing on buried persistent weak layers buried 3-4 feet deep around the 2/1 Rain Crust is not totally off the table.  To hedge your bets against this, avoid shallow snowpack areas, especially around rocky convex rollovers.  Remember what we said earlier in the season?  Don't trust a facet until it is swimming in the river.  We have just added over an inch of water weight to the snowpack.  Combined with the weight of the unlucky rider,  this could be enough to tip the balance in shallow rocky locations. 

This is a low-likelihood/high-consequence scenario and should be treated with careful consideration.  Before committing to consequential avalanche terrain on the north half of the compass, do your homework to evaluate the snowpack structure.  These deeply buried persistent weak layers will not provide you with obvious clues such as the collapsing or whumphing of the snowpack.  The only way to have greater certainty of whether this problem exists is to dig down to the layer(s) of concern and conduct a snowpack test.  

Set yourself up for success to have a great day in the mountains by using a conservative mindset, making a travel plan with wide margins, and always utilizing safe travel techniques such as only exposing one rider on slopes at a time, keeping eyes on them, and regrouping in zones that limit your exposure.  

Cornices are big right now and the spring is when they start to become weaker.  They can break further back than you think.   Give Cornices a wide berth, and use clues along the ridgelines such as trees and rocks to make sure you have solid ground below your feet.  

If you are out in the mountains, add value to your avalanche forecast by submitting observations here.  

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