Avalanche forecast

San Francisco Peaks / Kachina Peaks Wilderness

Kachina Peaks Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Highlights

A high wind event yesterday has left a possibility of wind slab avalanches in isolated locations, yet the greatest hazard continues to be persistent slab avalanches on steep slopes above treeline.  Avoid wind loaded starting zones on steep slopes and watch for cracking or whumpfing.  Challenging approaches and exits through thin snowpack and wind effected areas will continue to present a significant hazard.  

Avalanche problems

  • Persistent Slabs

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

    Faceted snow at the bottom of the snowpack remains the primary hazard on slopes of nearly all elevations and aspects.  This is a challenging problem to negotiate as it presents a low probability but high consequence scenario.  The exception is mid and low-elevation south-facing slopes, where snow coverage is minimal and solar radiation has reduced the early season snowpack.  Steeper slopes at high elevations present the most significant probability of being triggered.  Skiers and riders entering the backcountry should understand this hard-to-predict risk.  Ski one at a time, and stop in the safest zones possible.  Additionally, wind transported snow from yesterday may have loaded upper surface weak layers, and could result in small reactive soft slab avalanches.  Retreat from cracking slopes, especially those with terrain traps below traverses.

  • Wind Slabs

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

    North winds yesterday reportedly reached over 50 mph, with intermittent periods of wind in a more moderate range.  Some snow has likely been sublimated into the atmosphere, but some may have accumulated on the leeward side of gullies and ridges.  A rime event helped minimize some of this transportation.  Backcountry travelers should identify and avoid wind accumulated snow and the resulting berms, drifts and mounds.  Watch for cracking and be aware of hollow sounding snow--both obvious signs of instability.  

Avalanche Discussion

Yesterday's wind event may have slightly increased the avalanche hazard in isolated locations.  Human-triggered wind slab avalanches are possible on ridgelines and in cross-loaded gullies and slopes.  More consequentially, however, wind-deposited snow will increase the load on weak layers found near the top and bottom of the snowpack.  This will make these slopes more sensitive to a skier or rider triggering an avalanche.  It's probable that additional wind distributed accumulation is still not creating enough stress to trigger these weak layers, but on east, through some west facing aspects, where upper layers of the snowpack contain near-surface facets, small avalanches will be possible.  These small avalanches could carry a skier or rider over cliffs or into trees.  Be observant for cracking and retreat if slopes are showing signs of instability.

In other isolated areas, such as starting zones, this wind event may have further loaded and increased the weight on the basal facets found within the snowpack.  Today,  natural and human triggered avalanches in these areas are unlikely, but if an avalanche were triggered the consequences could result in a full burial.  Again, this is a low-probability but high-consequence scenario.  These additionally loaded slopes will be more likely to fail given a future storm event. 

Conditions are currently variable across the peaks. On Thursday, the Peaks received 2-7 inches of fresh snow and this was followed by moderate to strong winds.  Snow depths in Humphrey's Cirque range from just 55 cm on subtle ridgelines to over 160 cm in snow-drifted areas.  Riders and skiers are advised to descend with caution as numerous rocks and logs continue to be covered in some areas by just a few inches of snow.  On Thursday, an extended column test propagated on depth hoar on a southern-facing slope at approximately 11,500' at 10 cm from the bottom, demonstrating that there is at least a moderate level of propagation likelihood.  Additionally, a triple layer of crusts and facets is present in the upper snowpack on most southern-facing slopes. Below the first crust rests approximately 2 cm of near-surface facets overlaying an ideal bed surface.   In some locations, this layer has now been loaded by wind-transported snow and may fail under the weight of a single rider of skier.  Overall, the snowpack is showing poor structure, moderate strength, and moderate propagation propensity.

Thus far, no avalanches have been observed or reported this season.  This is due to the thin snowpack and the fact that slopes have yet to receive a significant snowstorm.   Egress and regress remain challenging, but they are starting to become more realistic and achievable with less effort.  The typical array of obstacles: boulders, rocks, stumps, and logs, are the primary hazard for those looking to earn some backcountry turns.  Be prepared to walk over some wind-affected terrain. and negotiate continued early season conditions.

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