Avalanche forecast

Avalanche forecast

Payette Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Triggering a persistent slab on weak snow from November remains unlikely. Recent snow and wind have formed small but reactive wind slabs above 7000'. 4-8" of snow today along with SW winds will likely create another round of reactive storm snow in wind-loaded terrain.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Yesterday, 2-4" of very light snow was observed from the recent storm. Winds transported this soft snow into shallow but dense wind slabs. NW winds shifted overnight to SW, so you can expect to find shallow wind slabs on any leeward terrain feature above 7000'. Yesterday, we received three different observations from people observing shooting cracks or unstable snow in wind-loaded terrain. Two of which were in the West Mountain zone. 

    Today, more snow is on tap with gusty SW winds. Expect new wind slabs to build again today. Look for clues like shooting cracks or active wind-loading around ridgelines. With a weak upper snowpack, new snow will likely not bond very well to existing snow surfaces. 

    (1/5/2024)

    Results from Tamarack Ski Patrol indicating sensitive cornice and reactive wind slabs

    Photo: Public

  • Persistent Slabs

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

    Triggering a persistent slab on weak facets from November remains unlikely. We are expecting a significant amount of snow in the mountains all of next week. This new snow will add a tremendous amount of weight (and therefore strain) to this weak snow near the ground. The old November facets have continued to show signs of strengthening. Are they strong enough to withstand next week's weather events? The ever popular answer from the snow and avalanche world is: it depends. That depends on how much snow we receive and how quickly. That depends on the location and strength of the old snow. The best advice to give is to avoid jumping right onto steep slopes during and right after a storm. Wait for the snowpack to adjust to a new load and remain skeptical of areas in the terrain where this weak snow is most pronounced (steep, north-facing terrain, above 7000').

    ADDITIONAL DISCUSSION

    Over the past week, we have noticed several weak layers in the upper part of the snowpack. Buried surface hoar has been found at multiple locations, buried several inches deep. We've also noticed facets that formed above and below some recent crusts. As this weak snow gets buried by more snow, it may become more reactive. Look for indicators of instability such as shooting cracks or collapsing (whumpfing). 

Avalanche Discussion

Yesterday, our forecast area received about 2-4" of new snow. Today into tonight, another stronger storm from the Gulf of Alaska could deliver 5-10" through Sunday. This pattern looks to continue for the upcoming week, with significant snow forecasted for our region and very cold temperatures. What does this mean for our lonely snowpack that has been sitting on the ground for months now waiting for its friends to grow? Read on to find out.

Although the facets from November have been slowly gaining strength, snow in the middle and upper snowpack have been losing strength. This week, we've found a myriad of weak layers in the mid to upper snowpack. Crust and facet combinations are buried just beneath the surface on many aspects. A fresh layer of buried surface hoar is hiding at upper elevations. At lower elevations, several inches of weak snow has formed in the middle to upper part of the snowpack during this dry spell. You can read my observation from yesterday here.  We are in the midst of a weather pattern change with consistent snowfall and colder temperatures. New snow means buried weak layers will undergo a strength test. Two important questions are: How much snow and over how much time? A lot of snow in a short period of time rapidly increases the likelihood of widespread natural and human-triggered avalanches. However, small amounts of snow over a longer period of time add a little bit a stress, a little stress, a little more, until it's too much. As new snow begins to fall this weekend and next week, what are impatient snow lovers to do? Remain vigilant. Pay attention to snowfall and weather changes. Watch for red flags like rapid loading. Look for obvious signs of instability like collapsing (or whumpfing) and shooting cracks. Of course, the best signs of instability are recent avalanche activity.

The best way for us to know what's happening as more people are out in the mountains is to submit an observation. Submitting an observation improves your skills, informs other users, and benefits avalanche forecasts. Simple photos highlighting conditions are very helpful.

Did you know there several avalanche classes this month specifically for motorized users? Check out our classes and events page to learn more.