Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

There is a lot of uncertainty with this storm, but Sunday will likely be a dangerous day in the mountains.  Heavy snow with a changeover to rain is a recipe for avalanches.  Make conservative terrain choices and avoid traveling on steep terrain.  Weak surfaces and a slick crust could make conditions especially touchy at higher elevations. 

Avalanche problems

  • Storm Slabs

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

    Expect that you could easily trigger large storm slabs at upper elevations on Saturday and that natural avalanches are also likely.  Avoid traveling on or under steep terrain.  Over a foot of snow will likely fall on slick crusts and weak surface hoar from Friday night.  Warming temperatures will add to the avalanche problem by creating an upside down storm slab with heavier snow on top of softer snow. 

    Terrain over 35 degrees, convex rolls, and areas exposed to the wind are likely spots to trigger an avalanche.  The wind may drift the snow into deeper slabs, so be particularly cautious to avoid steep slopes below ridgelines.  Look for warning signs like cracks that shoot away from you or recent natural avalanches.  You can also use quick hand pits and small, steep test slopes to see how easily the new snow slides on the crust.  If it slides off easily, that's a good sign avalanches are likely. 

    (12/1/2023)

    Small test slopes like this can be great indicators of unstable storm slabs. 

    Photo: Matt Primomo

  • Wet Slabs

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

    At some point overnight or in the early morning hours, snow will change to rain.  There is a lot of uncertainty with the timing of the warmup, the potential for freezing rain, and how much snow will fall before the changeover.  However the storm plays out, wet storm slab avalanches that slide easily on the underlying crust are likely.  These avalanches may be large enough to bury you, and the added weight of the water can make them more destructive than you may anticipate.  While wet slabs may be larger, wet loose avalanches will also be a concern, particularly at lower elevations where the new snow will fall on bare ground.  There is significantly more snow on the ground, and higher precipitation totals are forecasted to impact the western edge of the zone, like Salmon La Sac.  So, we expect the highest likelihood of large wet slab avalanches in these areas. With increased uncertainty, it is essential to dial back your terrain choices.  Choose simple terrain with low-angle slopes to enjoy the stormy weather.  Red flag signs for unstable wet slabs and wet loose avalanches are sinking past your calves in wet snow, rollerballs, and natural wet avalanches. 

    (12/6/2023)

    An example of a small wet slab that ran on the ground.

    Photo: Katie Warren

Avalanche Discussion

A complex storm system is already producing heavy snow throughout the East Central and will continue into Sunday. Expect fluctuating freezing levels, freezing rain, snow, and rain. We have a lot of uncertainty with this system, particularly with the timing. East Central could hold onto snow later into the morning on Sunday, meaning the likelihood of triggering avalanches could be the highest just as you venture into the mountains. With increased uncertainty, it's essential to dial down your slope angles, choose simple terrain, and give yourself large margins of safety.

We got a chance to get up above 6000ft in the Wenatchee Mountains near Mission Ridge on Saturday to look at surface conditions and the snowpack after last weekend's atmospheric river. While lower elevations have a thick melt-freeze crust on the surface, we found that all the rain didn't change the snowpack much at upper elevations in this area of the zone. Very weak snow exists on the base of the snowpack and is producing unstable snowpack test results. We also found the recent snow had a poor bond to the 12/7 crust and widespread surface hoar on top of the few inches of snow we received this week. With this weak structure, avalanche conditions could deteriorate rapidly and potentially linger for some time. While the Wenatchee Mountains can have a unique snowpack, this weak basal structure could exist in other areas of East Central. The surface hoar and weak bond with the 12/7 could be even more widespread throughout the zone. As you travel, you should carefully observe how well the new snow bonds to the underlying surface. 

New snow will likely fall on nearly bare ground at lower elevations. So, depending on where you go, the chance to hit buried rocks, logs, and other obstacles may still be a significant hazard. 

You can add to the forecast! Please let us know what you see in the mountains by submitting an observation.

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