Bollettino valanghe

Selkirk Mountains

Idaho Panhandle Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto last year. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

At upper elevations, be mindful of shallow wind-drifted slabs. On Friday, skiers easily triggered these fresh slabs running fast above the firm, old snow surface. You may encounter drifts around a foot thick on leeward-facing slopes below ridgelines and in gullies that could grow large enough to take you for a ride. Temperatures overnight dipped below freezing for the longest stretch since March 23, and this should help walk wet snow concerns back into the barn. Triggering a problematic wet slab remains a concern after significant meltwater made upper snowpack layers weak and rotten, and temperatures warm again Sunday under sunny skies. Stick to lower-angled slopes if you find a punchy snow surface.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    The latest round of snowfall delivered 3 to 5 inches across the Selkirk and Cabinet Mountains, and 1 to 2 inches in the Bitterroots - Silver Valley. As a result, shallow wind-drifted slabs formed above the firm old snow surface on northwest to north through southeast-facing slopes. Resting above the hard, partially refrozen old snow surface makes them particularly prone to avalanching.

    Slides triggered on Friday remained confined to the new snow, but traveled much faster down the slope than expected. If not paying attention to your surroundings in more complex or “no-fall” terrain, getting caught off guard could have a more dire consequence. Signs of freshly drifted slabs include surface cracking, wind etching, and lens-shaped pillowy snow. Manage your terrain to avoid areas below ridgelines and on steep convex rolls where your chances to trigger one of these drifts is elevated.

    (3/28/2025)

    Ski pressure on steeper slopes easily sheeted the new snow above the old, refrozen but breakable crusts. These were fairly predicatable and easy to manage, but traveled quick down the slope. Selkirk Mountains. March 28, 2025.

    Photo: Chris Bilbrey

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Elevations around 5,000 feet and lower finally experienced a solid refreeze Saturday night - at least 8 hours long across most of our forecast zones. This is the first prolonged period of below freezing conditions in 7 days. During that time, moderate to heavy rain and unseasonably warm temperatures pumped a significant amount of liquid water into the snowpack. Water pooling around harder layers or less permeable crusts helped weaken grain bonds and those layers got very weak and rotten. As a result, we observed many large to very large Wet Slab avalanches across all aspects and elevations.

    Cooler temperatures shutting off the water faucet will help reduce the wet snow threat, but there is always a lag time before we can write off these less predictable problems. As temperatures warm under sunny skies Sunday, pay attention to how quick the upper snowpack softens. This will likely happen faster on southerly-facing slopes where solar input is stronger. Frequently step off your machine or boards to assess how quickly the snowpack is softening, and avoid traveling on or below steeper slopes if you start collapsing into the snowpack - especially where rocks or vegetation are poking through the surface.

    (3/26/2025) Photo: Idaho Panhandle Avalanche Center

Avalanche Discussion

Springtime can offer a great opportunity to travel around the mountains with a bit less fear, and allow us to step into terrain that is typically off-limits during most of the winter. One part of spring that often doesn’t happen in the winter is the dramatic minute-by-minute to hourly weather swings - one moment it’s sunny and hot, and you're sweating profusely. Then the next, it’s cold and snowing, and you’re having to put on a layer. These wild fluctuations require us to manage both dry and wet avalanche problems that can evolve much quicker than we anticipate - primary drivers being how long the sun is out or how long it snows. Just because you encounter tricky or muddy trailhead logistics, or you see budding flowers and green grass in the valley’s, you still need to be thinking about avalanche hazards in the mountains.

With the return of cooler temperatures, our Wet Slab avalanche threat will slowly lose its bite, but can hang around or come back into striking distance with little notice. The main wetting front from last week's rain and HOT temperatures that made a weak, manky mess of the upper snowpack has likely traveled deeper or to the ground. Places where water got hung up will likely refreeze during long periods of below freezing temperatures and lock up those instabilities. However, as we flip the calendar closer to April, the sun angle gets higher in the sky and this can have a profound influence on reemerging wet snow hazards - even thawing refrozen meltwater closer to the surface. Be wary of slopes with large glide cracks as the amount of water moving through the system could nudge these slopes closer to failure as the barrier between the ground and the entire snowpack gets lubricated like a slip-n-slide track. Glide avalanches are unpredictable at best to forecast.

The dueling battle of warm versus cold air enhanced by orographic lift when storms move through can lead to intense periods of snowfall, and rapid accumulations. Depending on the type of older snow surface the new snow falls on will have a big influence on bonding and how sensitive fresh slabs are. Use surface clues of unstable snow and non-consequential test slopes to set yourself up for success and identify areas of slopes to simply go around. Stepping into more complex or extreme terrain still requires cautious snowpack assessments and decision-making where even a small, more isolated slide can lead to a bad outcome.

Lastly, fresh snow can be like adding another glass of water to the saturated ground, and it doesn't take much new snow warming under sunny skies to increase the chances to trigger a wet avalanche. More new snow often equals larger wet snow slide potential. Frequently assess surface wetting as you move up and down in elevation as you will likely not find conditions to be the same down in the mature timber as higher up, and vice versa. Now is a great time to take advantage of longer days and get out on longer tours or rides. Consider exiting the mountains early if conditions change faster than you anticipate, or you start seeing fresh evidence of natural activity.

**Eastern Oregon University is conducting a survey to better understand avalanche safety preparedness among motorized backcountry users. The survey will help us learn more about who is purchasing, and practicing with avalanche rescue gear (beacon, probe, shovel) and participating in avalanche education—and why some riders are not. The survey is confidential and anonymous. Your feedback is invaluable to improve avalanche education and awareness across North Idaho and Northwestern Montana. Please take a moment to share your experience and help your local avalanche community. You can take the survey HERE.**

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