Boletín de aludes

East Cabinet Mountains

Idaho Panhandle Avalanche Center
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Peligro de aludes

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

Lo esencial

Heavy, wet snowfall Monday will transition to heavy rain overnight. A potent atmospheric river characterized by near-historic moisture will introduce a “firehose” of moisture into North Idaho and Northwestern Montana. The rain line will rise to around 7,000 feet overnight Monday and will saturate recent snowfall and buried weak layers, and could provoke a widespread cycle of avalanches large enough to bury, injure, or kill a person. Some of these avalanches could release naturally, and it will be very easy for backcountry travelers to trigger them.

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
    Possible
    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 cycled follow a high elevation rain event. We expect similar conditions to develop tonight. But with a significantly deeper snowpack now, We are inticipating much larger avalanches.

    Photo: Jackson George

Avalanche Discussion

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.

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 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.

If warmer air arrives sooner than expected and rain starts wetting the snow surface higher up, wet snow hazards will likely emerge quickly. Plenty of cold, dry snow sits in the top one to two feet below the surface and rain wetting these layers will help to weaken individual bonds and promote natural sluffing in steeper terrain.

Despite the much-needed recent snowfall, coverage remains thin, particularly at lower elevations and on southerly-facing slopes. 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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