Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

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

Very dangerous avalanche conditions are expected to develop by the afternoon as snow, wind, and rain overload a dry snowpack. Where the snow remains dry up high, it will be wind-affected in exposed terrain and likely unstable. Once the rain starts, avoid terrain where avalanches can start, run, or stop.

Avalanche problems

  • Wet Slabs

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

    Snow transitions to rain below approximately 6000 ft in the early afternoon on Sunday. The snowpack will rapidly deteriorate as liquid water enters it. Avalanches could take on various forms: wet loose, wet slab, or even glide. You might see cornices sag and collapse. If water seeps down far enough to reach weak layers buried deep below, a very large persistent slab avalanche could occur (see below for more details). Regardless of what you call them, you’re not going to want to hang out on or below large paths where slides could grow large enough to bury or kill you. Be wary of precariously hanging blocks of snow that might break above or below you.

    Until water has time to drain out or refreeze, avalanches will be of concern. Be aware of steep terrain overhead where avalanches can start, and don’t linger in terrain traps where avalanche debris can concentrate. When it starts raining, get out of avalanche terrain. Avoid it until the snowpack has fully refrozen. At lower elevations where the snowpack is lacking in many areas, the likelihood of encountering a dangerous avalanche will be slightly lower.

    (3/2/2025)

    A wet slab avalanche that crossed the Hart's Pass road in the East North zone earlier this month.

    Photo: Katie Warren

  • Wind Slabs

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

    Precipitation will fall as snow on Saturday night down to lower elevations and continue to fall as snow at upper elevations throughout the day, primarily closer to the Cascade Crest. This storm will be accompanied by moderate to strong wind. Small and fresh wind slabs will form overnight and continue to build up high throughout the day. Older and deeper slabs that were reactive on Saturday may still harbor some sensitivity, and triggering one could create an avalanche large enough to bury you.

    Wind slabs typically form just below ridgelines and in gully or chute-shaped terrain features. Look for clear signs of wind transport: dune-like drifts, cornice formation, and blowing snow. As you move about the terrain and the snow begins to feel denser and look unevenly distributed, assume wind slabs probably lurk nearby. Long shooting cracks, collapsing, and recent natural slab avalanches are very good reasons to avoid exposed terrain steeper than 35 degrees.

    (3/21/2025)

    Signs of wind affected snow and potential wind slabs. 

    Photo: Dallas Glass

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    In the north and eastern portions of the zone, you may still be able to trigger large avalanches on an old, weak layer about 3 feet below the surface. The snowpack is shallower, and the layer is more well-developed near and east of Harts Pass and Mazama. Further west, near Washington Pass and Rainy Pass, these avalanches are unlikely. 

    That said, the current gusty storms are adding enough stress to the snowpack that we can't write off persistent slabs altogether. Furthermore, rain on snow could reawaken this beast if liquid water works its way all the way down to weak snow. You can deal with this low likelihood, high consequence situation by avoiding steep northerly slopes with shallow and variable snow cover in the eastern part of the zone. You can dig profiles and use snowpack tests (deep tap and propagation saw tests) to identify the weak layer. When in doubt, defer to lower-angle slopes and simpler terrain.

    (3/17/2025)

    A widely propagating avalanche near Tiffany Mtn.

    Photo: Willie Webster

Avalanche Discussion

You might be able to gently tip-toe around steeper terrain in the morning on Sunday. There will be new,  dry snow at all elevations. But unless you plan to be back to the trailhead while some of us are still sipping on our morning coffee, you'll want to be sure you have an exit strategy that keeps you well out of avalanche terrain. Conditions will swiftly decline with the onset of rain. Furthermore, storm slab instabilities may also exist in more sheltered terrain. Conditions will be less hazardous further east, where less precipitation of either form is expected.

Recent storms have totaled over 2 feet near Washington Pass, with less further east in the zone. Throughout the past week, observers have reported a number of small natural and triggered wind slab avalanches. Many were small (D1), but a number of avalanches were big enough to bury or kill a person (D2).  These occurred in both leeward, wind-loaded slopes as well as sheltered terrain. Yet another report of someone getting caught and carried in a wind slab avalanche came through down in Steven's Pass. That makes 6 involvements in the last 10 days.

An old weak layer (the January Drought Layer) is buried 2–3.5 ft (70-120cm) below the surface but shallower east of Mazama. Near Rainy and Easy Passes, the JDL is over 4 feet deep and capped with a thick melt-freeze crust. In many parts of the zone, the JDL has rounded and gained strength. However, in the past week, observers have continued to report snowpack tests that have produced sudden and propagating results on Silver Star Mountain and near Harts Pass. On March 17, an observer near Tiffany Mountain reported widely propagating recent natural avalanches and rolling collapses on a weak layer in the middle to lower half of the snowpack. Then, on March 22nd, another observer documented a recent natural slab avalanche near Mt. Tiffany that looks deep enough to have potentially released on the JDL.

NWAC Forecasters visited the site of the avalanche fatality near Harts Pass that occurred on 2/28. You can read the initial observation here. 

Submit an observation to the website or the Avy App to help NWAC Forecasters reduce uncertainty. It can be short, simple, and even anonymous. 

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