Avalanche forecast

San Francisco Peaks / Kachina Peaks Wilderness

Kachina Peaks Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

It has been more than 24 hours since two large storms deposited three to four feet of snow, loading the existing weak layers and creating wind slabs. The likelihood of triggering an avalanche has decreased; however, it remains elevated. Backcountry travelers are likely to trigger small to very-large avalanches on steep slopes near and above treeline that could have significant consequences.

Travelers should avoid steep slopes, pockets of wind-loaded terrain near ridgelines, and areas of widespread wind deposition, such as cross-loaded gullies and starting zones. 

Avalanche problems

  • Persistent Slabs

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

    In areas that possessed a snowpack, prior to the arrival of our last storm, two primary persistent weak layers have been buried deep below the surface. The highest in the snowpack is a small (~2cm) melt-freeze crust that developed during January and is surrounded by facets and near-surface facets. The second persistent weak layer is at the base of the snowpack where the early December snow has faceted creating a layer of basal facets and depth hoar. Prior to the storm, these layers had moderate to high propagation propensity and continue to be a concern, especially in areas with thinner snowpacks (<2m) where a traveler's weight could trigger an avalanche on this weak layer. If triggered, expect the avalanche to propagate in surprising and unpredictable ways with a possible crown height of 4'-7', making this problem especially difficult to manage.

    The best way to manage the risk from persistent slab avalanches is to make conservative terrain choices. Persistent slabs can be potentially triggered by a skier’s/boarder’s weight, even weeks after the last storm.

     

    (2/4/2024)

    Snowpit displaying reactivity at persistent weak layers prior to the recent storm.

  • Wind Slabs

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

    Winds near treeline have stayed in the moderate zone, while ridgetop gusts have been stronger.  There has been widespread snow transportation at all elevations, and many leeward slopes and ridgelines have experienced significant loading.  Avoid loaded starting zones, wind drifts, mounds of snow, pillowed areas, and cornices.  If large enough, a wind slab avalanche could step-down and release a persistent slab avalanche buried deep in the snowpack.

    A large (D2) natural avalanche released on a northwest aspect in the Upper Bowl while it was closed, likely during the last pulse of moisture (2/8/24). The starting zone for this avalanche was heavily wind-loaded due to south-southwest winds during the storm. This avalanche was large enough to injure, bury or kill a person.

    Natural large (D2) avalanche on a northwest aspect loaded by south-southwest winds in the Upper Bowl while it was closed.

    Photo: Tanner Porter

Avalanche Discussion

Storm totals during the end of the week ranged between 39" and 55" of snow.  Over 5" of SWE has been recorded at the Snowslide Canyon  Snotel site since the storm's beginning. On  Friday, a short window of visibility was available and revealed debris from numerous natural avalanches that released during the storm. The first was likely a wind slab avalanche, occurring on a northwest aspect in the Upper Bowl, while it was closed, likely during the most recent moisture pulse (2/8/24). In addition to this avalanche, several older debris piles were noted within the Humphreys Cirque on east and southeast aspects. Due to significant weathering, it was challenging to estimate when, during the storm, these released and the size of these avalanches.

As mentioned previously, two primary persistent weak layers are the focus of concern. The first is a set of persistent weak layers, facets, and near-surface facets located above and below various melt-free crusts.  The continuity of these layers has been hard to assess, but if present continuously in the snowpack, these layers could also result in large avalanches. The second of these layers is a set of basal facets and depth hoar buried at the bottom of the snowpack. This layer has been found most commonly across many aspects.  Its presence seems widespread except in some south-facing areas where snow has melted off between storms and other high-terrain areas where snow has been significantly stripped by wind. 

Assessments on Friday (2/9/24) and Thursday (2/8/24) showed the wind slab to be reactive in extremely isolated pockets with the majority of wind slab being stubborn to non-reactive. Additionally, on Thursday (2/8/24), an ECTP24 was recorded that failed on 2-4 mm of chained depth hoar at the bottom of a shallower (110cm) NNW slope.  

Winds have been variable and intermittent during different phases of the storm. At upper elevations, snow depths are highly variable with some aspects and slopes completely stripped, while other areas became loaded by wind. Wind slabs are expected to continue to build today.  Use appropriate spacing when traveling and avoid wind drifted locations.  Retreat or find a different route if cracking or shearing is observed.  

Cold temperatures and severe wind chills are expected today.

Note that the snowpack depth and layers were quite variable pre-storm.   For those seeking more information, please view the observations page.  https://kachinapeaks.org/Observations/#/view/observations.   You can also check out the snowpits published this week at snowpilot.org.

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