Avalanche forecast

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Avalanche danger

Tue
Alpine
4 · High
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

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.

Avalanche problems

  • Persistent Slabs

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

    Since the beginning of a significant storm cycle that started on December 4, the Silver Valley-Bitterroots have picked up nearly 2 feet of snow. This new snow fell on a weak snowpack, with several layers of concern. At the base of the snowpack, rotted early-season snow has faceted and weakened over time. North and east-facing aspects are the most likely areas to encounter a snowpack that has old snow and connects different terrain features. The slab above this old snow is already 2-3 feet deep and will continue to grow in size with new snow today. Due to the depth of these worrisome layers, avalanches that fail on a persistent weak layer will be large and dangerous and could bury 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 or near avalanche terrain is not recommended, and the danger will increase as the rain totals increase during the day.

    Snowpit from a northeast-facing slope at 6300'. Since November 30, when this snowpit was dug, 2-3 feet of snow have accumulated on top of the weak old snow interface, where faceting developed. 

    Photo: Izzy Davis

  • Storm Slabs

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

    Snowfall over the last 4 days has been heavy and wet, and this new snow has fallen on lighter-density, weak snow. This combination has created an “upside-down” snowpack, and more snow and water will be added today as an atmospheric river enters the region. With a significant amount of weight being added in a short period of time, conditions will change quickly and push the different storm interfaces to failure. It will be easy for backcountry recreationalists to trigger a dangerously sized avalanche, and natural avalanches are likely. An avalanche that fails within the storm snow has the potential to step down deeper in the snowpack, creating large avalanches that could connect nearby slopes and terrain features. Avalanches may run far into runout zones, and debris could reach lower-angle terrain.

    Several different resistant planar breaks in the upper 1 to 2 feet of recent storm snow, failing with moderate to hard force. These interfaces will become more reactive with the addition of heavier snow and rain.

    December 7, 2025. 

    Photo: Izzy Davis

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    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 following 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

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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