Avalanche forecast

Salmon River Mountains

Payette Avalanche Center
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Avalanche danger

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

Heavy, wet snowfall, valley rain, and strong winds will create very dangerous avalanche conditions. The likelihood of large natural and human-triggered avalanches will increase dramatically as the storm continues, peaking late today. Expect to encounter a range of storm-related avalanche problems, including wind slabs, storm slabs, and loose snow avalanches. Weak layers buried beneath 2-4 foot slabs may produce very large avalanches. Rain and warm temperatures at lower elevations will bring on wet snow problems this afternoon. Travel in avalanche terrain is not recommended. Some avalanches may impact roadways or trails below steep slopes in the valley bottom.

 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    Today's wet-and-wild storm—with heavy, dense snowfall, valley rain, and strong winds—will overload a snowpack with multiple weak layers. As the storm progresses, these layers will be buried beneath a dense 2-4' thick slab. Any slide you trigger today could be large enough to bury you. 

    Yesterday, I found both weak layers in a snow pit at 6,500 feet in the Salmon River Zone, buried about 1' deep and 2.5 feet deep, respectively.  Though they have trended towards being stubborn or difficult to trigger and are becoming increasingly isolated in terms of where they can be triggered, this storm will actively re-test any strength this snow has gained. Areas at middle and upper elevations that have both layers buried more shallowly will be the suspect slopes today. Note that both zones are large and retain some area-specificity. For example, well-preserved surface hoar is buried quite shallowly near Big Creek, while more northern portions of the Salmon River Zone have received more snowfall, compacting this same weak snow layer and making it less of an issue. 

    Avoid traveling on or beneath avalanche terrain by late today—slopes steeper than about 30 degrees. Pay close attention to the slopes above you and don't travel in the runout zones of avalanche paths.

  • Storm Slabs

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

    Natural and triggered avalanches are very likely to occur within the accumulating storm snow. Even without the buried weak layers described above, avalanche conditions would still be dangerous. Storm slabs will be most common on middle- and upper-elevation slopes that are being drifted by today's strong winds, but could also occur on steep, wind-sheltered slopes. Avalanches will be larger where wind drifts incoming storm snow deeply. Lower- and middle-elevation slopes at the snow/rain line may be particularly susceptible to storm-snow instabilities, and see a mix of rain and snow. These avalanches could trigger deeper weak layers (described above), producing much larger avalanches.

    WET SNOW AVALANCHES: Wet snow slides are possible on slopes above the valley floor—especially if rain is falling. The scope of these slides may range anywhere from 5,000 to 7,000 feet today. 

Avalanche Discussion

Today's avalanche conditions will be closely tied to the weather forecast, and we all know how fickle those can be. They are doubly so when warm temperatures, fluctuating snow lines, and rain are in the mix. What rings true is the age-old adage: Weird weather produces weird avalanches. 

Rewind to a few days ago. Persistent weak layers remained a concern throughout our forecast area. Today's avalanche conditions are more complex—especially if you try to predict what type of avalanche will occur. Will it be a sneaky 2-4' thick persistent slab that released in a well-connected, broad start zone? Will it be a somewhat smaller, 1-2' thick persistent slab that breaks on a more recent weak layer that remains well-preserved on a middle-elevation terrain trap? Or how about a slab of moist snow that oozes down a steep slope above the valley floor? Who knows—I can't say that I do with a high degree of confidence. But I do know that avalanche conditions will be western out there today. When the going gets complicated, the best approach is to simplify: avalanches of some variety are very likely today, and they could be very large. When conditions like this exist, the travel advice is also simple: avoid traveling on or beneath slopes steeper than 30 degrees, including road cuts and the runout zones of small but steep features.

Note that Warm Lake Summit Road will remain closed for the next 24-48 hours. 

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