Boletín de aludes

East Cabinet Mountains

Idaho Panhandle Avalanche Center
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Peligro de aludes

Wed
Alta montaña
4 · Fuerte
Límite del bosque
4 · Fuerte
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 9 months ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Very dangerous avalanche conditions developed overnight and will last though Tuesday as heavy, wet snowfall transitioned to heavy rain along with strong winds. A potent atmospheric river characterized by near-historic moisture is introducing a “firehose” of moisture into North Idaho and Northwestern Montana. The rain line rose to around 7,000 to 7,500 feet overnight Monday and will saturate recent snowfall and overload pre-existing weak snow layers. It will be very likely for backcountry travelers to trigger avalanches and natural avalanches are likely. Avalanches can break wide across terrain features and run long distances to lower elevations.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2–3

    Since the beginning of a significant storm cycle that started on December 4, the northern mountains have picked up nearly 2 feet of snow. This new snow has beein incrementally loading on top of a weak faceted midpack, with several layers of concern. In the lower half of the pack, rotten early-season snow has faceted around a hard crust. The old hard crust is thickest and most connective across terrain features on north and east-facing aspects, however the same general structure is found around the compass above about 5,000 feet. The slab above this old snow is already 2-3 feet deep and will continue to grow in size with additional snowfall today. We might be nearing the tipping point later today, and due to the depth of these worrisome layers, avalanches that fail on a persistent weak layer will be large and dangerous, and could bury, injure, or kill a person.

    Avalanches that fail naturally or are human-triggered could break wider and run further distances down slope than expected. As snow transitions to rain and liquid works its way deeper into the snowpack, slopes over 30 degrees will start to come “unglued” and create very dangerous avalanche conditions. Traveling on, near, or below avalanche terrain is not recommended, and the danger will increase as the rain totals increase during the day.

    (12/3/2025)

    Despite the snowpack still unseasonably shallow, even at the higher elevations, avalanche start zones and tracks are becoming more filled in and connected. This is helping increase potential avalanche size with the next round of heavy snowfall and rising snow levels. Selkirk Mountains. December 3, 2025.

    Photo: Chris Bilbrey

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Very Likely
    Tamaño
    2

    Over the last 5 days, a strong winter storm cycle moved across the Idaho Panhandle, delivering 16 to 20 inches of snow and 2.5 to 3.5 inches of SWE (snow water equivalent).  An additional 8-10 inches  of heavy dense snow may fall today accompanied by an uptick in winds. Up until yesterday evening, wind speeds had remained relatively calm, leaving ridgetops now fully loaded with ample storm snow for transport. With wind speed ramping up, expect to find thicker and more sensitive slabs on the lee side of ridgelines.

    Snowpack instability is possible anywhere a cohesive slab has formed over a softer, weaker layer. With the gradually increasing temperatures of this storm cycle, this set up is more than likely present. Quick assessments, such as hand pits or small, safe test slopes, can provide valuable information about how the new snow is bonding. Shooting cracks, recent avalanches, or other obvious signs of instability are clear indicators to steer toward lower angled slopes and avoid all avalanche terrain,

    (12/7/2025)

    Several different resistant planar breaks in the upper 1 to 2 feet of recent storm snow, failing with moderate to hard force.

    December 7, 2025. 

    Photo: Izzy Davis

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    As the snow line works its way up the mountain with rising temperatures and transitions to rain, liquid input to surface snow will create wet loose avalanches. Steep slopes, gullies, and cliffs are the most likely areas to encounter this problem. Seeing rollerballs that gain in size or sinking to your boot top in heavy, wet snow are red flags that this problem is materializing. Due to the amount of new snow at mid and lower elevations recently, wet loose avalanches could quickly gain in size, and run far distances down slope as they entrain more snow. Avoid travelling under any overhead hazard, and give yourself wide margins near cliff bands and chutes.

    Earlier in the season, a small avalanche cycle followed a high elevation rain event. We expect similar conditions to develop tonight. But with a significantly deeper snowpack now, We are anticipating much larger avalanches.

    Photo: Jackson George

Avalanche Discussion

Today's advice is simple...avoid avalanche terrain. Weird weather breeds weird avalanche behavior

Snow totals over the past 24 hours range 7 to 13 inches across the Selkirk Mountains, and East and West Cabinet Mountains, 5 to 9 inches in the Silver Valley area, and 4 to 7 inches in the Purcell Mountains. Once the  warm tounge of air arrived Monday night, precipitation flipped to rain. Weather stations in the Selkirk Mountains, and East and West Cabinet Mountains report 1.5 to 3 inches of rain in just shy of 12 hours. Silver Valley stations report 1.5 to 2 inches of rain, and generally 0.5 inches is reported across the Purcells. Hawkins Lake just south of the Canadian border is the only site that we suspect didn't receive rain.

There’s a saying in the avalanche business…”your avalanche forecast is only as good as your weather forecast”. As we enter into a period of challenging weather forecasting, it’ll be important to think one step ahead and be willing to make adjustments around your terrain selections. With somewhat limited field observations and number of eye popping test results, there is a fair bit of uncertainty around how much snow volume or water load is going to kick buried weak snow layers into a more reactive state, or provoke a natural avalanche cycle.

One thing we do know is that a worrisome structure exists in the upper snowpack - primarily focused to mid and upper elevations. Multiple faceted mid-storm crust and a layer of larger facets above the wetted now refrozen early-season snowpack highlight the main concerns. Throw in buried surface hoar on north through east-facing slopes - so far discovered in the Silver Valley and West Cabinet Mountains - and we have a multitude of layers to wreck havoc on backcountry recreation.

Although observations have yet to report many propagating results in Extended Column Tests, snow safety teams have had better luck producing avalanches with explosives. These results, while within an operational area, are fairly representative of the potential behavior of a wild snowpack, and a forward context of the lurking danger below. Despite the lack of propagating results, Compression Tests have repeatedly failed with moderate force in any one of these buried layers of concern. Now stack thick dense and/ or an inverted slab on top and the added weight of a rider or machine may be what’s needed to nudge the snowpack over the edge.

Despite the much-needed recent snowfall, coverage remains thin, particularly at lower elevations and on southerly-facing slopes. Heavy rain Monday night may have erroded lower elevation snow cover and access. Additionally, early-season hazards—rocks, stumps, downed trees—are lurking just beneath the surface. Invisible enough to catch you off guard, shallow enough to abruptly end your day if you’re skiing or riding fast, or lead to a bad outcome if you get knocked off your feet in a slide.

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