Avalanche forecast

Blues

Wallowa Avalanche Center
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Avalanche danger

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

Avalanches are likely to be triggered by a rider today within the new snow, especially along exposed ridgelines where the wind will deposit new snow into dense wind slabs.  The new snow sits above a wet snow surface at most elevations and avalanches could become larger and more destructive if they entrain wet snow.  Conservative decision-making should be utilized today while avoiding wind-loaded slopes and assessing the reactivity of the new snow.

This forecast is sponsored by CB Construction, Inc. 

Avalanche problems

  • Wind Slabs

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

    New snow and accompanying winds will blow snow into sensitive wind slabs in exposed terrain, especially along ridgelines.  Yesterday, the winds were light with moderate gusts and mostly out of the South.  There was enough new snow available to be transported into small wind slabs.  Additional snow overnight and more today will be blown by West/Northwesterly winds.  A variety of aspects in upper elevation terrain will form sensitive wind slabs throughout today.   Look for clues to wind loading such as rippled texture to the snow, cracking around your skis or machine, and pillows of snow deposited downwind from stripped locations.   Use small and inconsequential test slopes no taller than a two-story house to test the reactivity of wind slabs.  Avoid wind-loaded slopes today. 

    At all but the highest elevations yesterday, the new snow has fallen onto a wet snow surface that was observed to be loose and not cohesive.  A wind slab that is triggered has the potential to entrain wet snow and make the consequences of an avalanche greater.  Avalanches entraining wet snow can be very destructive.  

  • Storm Slabs

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

    In areas that are protected from the wind, the potential for rapid snow accumulation will make avalanches within the new snow likely.  The storm snow that started on Wednesday afternoon transitioned from rain at lower and mid-elevations, and observers in the Northern Wallowas and Elkhorns noted that the new snow was bonding well to the old (wet) snow surface.  That being said, localized rapid snow accumulation throughout the forecast area could create sensitive slabs of new snow.  Throughout your travels, use hand pits to dig down to the old snow surface to see if the new snow is settling into a cohesive slab and how well it is bonding at the interface.   Ski or ride across small inconsequential steep test slopes to see how the new snow is reacting.  If you are finding slab development in the new snow that is reactive, avoid traveling on or underneath slopes greater than 30 degrees.  

    Just like the wind slabs discussed above, storm slabs have the potential to entrain wet snow if they are triggered or released naturally.  Any new snow avalanche that entrains wet snow will be difficult to escape and could have dire consequences.    

    In areas where the snow is not settling into a storm slab, Dry Loose avalanches will be likely in terrain greater than 35 degrees.  Avoid getting caught up in a dry loose avalanche, especially where it could push you over consequential terrain such a cliff bands, or into a terrain trap. 

    (1/11/2024)

    Storm Slabs failing on a density change in the new snow. 

    Photo: Caleb Merrill

Avalanche Discussion

Winter has made a return to the mountains of Northeastern Oregon.  Wednesday brought rain on snow after several days of very warm temperatures and strong solar input that melted the snow surface.  Temperatures slowly cooled, but not enough to produce a firm crust on the surface at most elevations.  Precipitation transitioned from rain to snow.  Today and tonight will bring an additional load of snow to our snowpack and will need some time to adjust to this new weight.  The new drier snow on a wet cohesionless snow surface creates an added level of uncertainty as to how avalanches may react.  Wet snow is hard to assess.  If you question your ability to assess these conditions, then sticking to terrain less than 30 degrees is recommended.  

As of this morning, storm totals since Wednesday are looking like this: 

In the Northern Wallowas: 10-12" with a snow water equivalent of 1.5"

In the Southern Wallowas: 8-10" with a snow water equivalent of .7"

In the Elkhorns: 6-8" with snow water equivalent of .5"

In the Blues: 4-6" with snow water equivalent of .7"

Today, another 3-8" of snow is expected with an additional 3-8" tonight.  It is a good time to reset your travel mindset and take a step back.   Create a well-thought-out travel plan that provides wide terrain margins.  Discuss what you are seeing with your partners.  Listen to your gut, and make conservative decisions. If you decide to enter avalanche terrain, travel one at a time, keep eyes on your partners, and regroup well clear of avalanche runouts.   

Check out a couple of yesterday's observations from the Northern Elkhorns and Northern Wallowas here and here.  

Cornices have grown dangerously large and recent warmer temperatures have weakened them.  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 or machine. 

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Deeper Persistent Weak Layers: 

We have several crusts with weaker snow around them buried up to 5-6 feet deep in the snowpack.  There is also an isolated layer of surface hoar that has been noted in the western Wallowas and northern Elkhorns buried 3-4 feet deep.  These weak layers have not been producing reactivity in snowpack tests, but there remains the off-chance that a new snow avalanche could produce enough weight to "step down" to one of these layers.  Pro Observer Tom Whipple found the layer of surface hoar in the Elkhorns yesterday, buried 3 feet down, and non-reactive in snowpack tests.  See his observation here.  

To hedge your bets against awakening one of these monsters, avoid shallow snowpack areas in very steep, alpine rocky terrain.

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New snow at the lowest elevation band in the Blues (3000-4000') has fallen on bare ground.  While the new snow will not create avalanche issues at this elevation, a significant hazard will be in the form of shallow-covered obstacles.  

Regions covered