Avalanche forecast

Avalanche forecast

Payette Avalanche Center
View on map

Avalanche danger

Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A layer of buried surface hoar has been producing numerous human-triggered avalanches 1-2 feet deep within the past 48 hours. You can encounter this avalanche problem in steep, wind-loaded terrain as well as wind-protected areas at middle and lower elevation. A deeper persistent avalanche on old snow near the ground is unlikely but could be large and destructive.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2

    A persistent weak layer of buried surface hoar is buried 30-45 cm (12-18") beneath the surface. We've found this layer of buried surface hoar in usual places:

    • East aspect near ridgelines
    • Northern wind-exposed aspects 
    • We've had reports of reactivity on southern aspects
    • Wind-protected areas at middle elevation

    Given the widespread nature of this persistent weak layer and how reactive it is (touchy), human-triggered avalanches are likely on this buried surface hoar. Unfortunately, there are no x-ray goggles available that enable you to see where buried surface hoar is and where it isn't. Because of the unpredictability of this avalanche problem, avoiding slopes steeper than 30 degrees is the only way to avoid triggering an avalanche on this layer of buried surface hoar.

    Additional Discussion: You are most likely to encounter this avalanche problem in areas where dense, wind-deposited snow sits atop buried surface hoar. We've had numerous reports of wind slab avalanches running on buried surface hoar since Wednesday (observation 1 and observation 2). That is not the only area where you will find this problem though. We've also had reports of softer slab avalanches in wind-protected terrain (see observation here).  

    (12/23/2022)

    Remotely-triggered avalanche on buried surface hoar (north-facing aspect)

    Photo: Studley

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–2.5

    On Wednesday, in the West Mountain zone north of Tamarack Resort we found a more shallow snowpack on an east aspect.  This persistent weak layer is widespread throughout all aspects and elevations. In other parts of our advisory area, the snowpack is deeper and has not shown consistent signs of instability on this weak layer. Although unlikely, an avalanche on this weak layer would be large and destructive. It would take a lot of force to initate an avalanche on this weak layer, the weight of a person may not be as likely as the weight of a snowmachine. You are most likely to encounter this deep persistent slab problem in areas on or around steep slopes where the snowpack is thin (think trigger points around rocks). 

    We've been talking about this layer of persistent facets near the bottom of the snowpack for nearly three weeks now. Given the widespread nature of this persistent weak layer and the poor snowpack structure, this problem should not be completely removed from your mind. Why Deep Persistent now?

    • Although this problem did not become deeper , this persistent weak layer is buried 2-3 feet near the bottom of the snowpack
    • Another, more pressing persistent weak layer (see problem above), has become our primary persistent slab problem. This layer of buried surface hoar is much closer to the surface.
    • This November drought layer was buried nearly three weeks ago, but has not given us reason to believe it would not be reactive given the right circumstances.

Avalanche Discussion

Today's avalanche forecast is sponsored by Mile High Powersports of McCall. Thank you for supporting the Payette Avalanche Center.

We've been in a steady trend of considerable avalanche danger since earlier this week. A well preserved layer of surface hoar was buried on Sunday and has been the source of numerous human-triggered avalanches within the past two days. At upper elevation terrain, dense, wind slabs are resting atop this layer of buried surface hoar and if you encounter this setup on a steep slope, the likely result is an avalanche. At middle and lower elevation, avalanches have been reported in wind-protected areas. Older snow from November buried near the bottom of the snowpack has recently displayed the ability to propagate with moderately hard force. Coupled together, we have two persistent weak layers buried in our snowpack. One that will be at the forefront of our minds with obvious signs of instability, the other, deeper problem cannot be completely ruled out. These avalanche problems should keep people away from avalanche terrain today. 

 

Check out our observations page to read reports of recent avalanche activity