San Francisco Peaks / Kachina Peaks Wilderness

The potential for a skier or rider to be caught in a persistent slab avalanche complicated by wind slab remains possible today.  Conditions on the San Francisco Peaks are unordinary, and these unusual conditions deserve conservative decision making.   Backcountry travelers are advised to avoid steep slopes with hollow sounding wind slabs and starting zones in rock-lined chutes.  The danger rating remains moderate for all aspects and elevations near and above treeline.   

On Wednesday, two D1.5-D2 avalanches were triggered on the peaks.  One was human-triggered (HS-ASr-R1D2-I), the other artificial (HS-AEc-D1.5-R3-S); and, the aspects were nearly opposite, one on an east-facing slope and one more west-facing, but both ran on steep above treeline terrain.  Both are evidence of the varying primary and localized wind directions and speeds associated with the St. Patrick's storm and the widespread effect it had on the snowpack. The artificially triggered D1.5 was the result of control work conducted by Arizona Snowbowl ski patrol within the ski area boundary while the bowl side of the ski area was closed for mitigation operations.  It measured approximately 150' x 400' with a crown height of 8-10”.  The second was remotely triggered on the skin track out of the Humphrey's Cirque and measured approximately 30' x 75' with a crown height between 12-24".   Much gratitude to those who promptly submitted photos and observations of this event.  

This second event is an outstanding reminder of the inherent hazards associated with our standard and unique travel patterns on the San Francisco Peaks.  Typical skin tracks exiting the Inner Basin back into the west side often traverse steep terrain, sometimes above rocks and cliff bands.  This, along with our common top-down access, can limit our slope assessment, add pressure to our judgment, and overall create an environment of challenging and complex risk management and decision-making.  

The avalanche hazard is expected to remain steady today, and it is possible that additional avalanches may be triggered.  Cold overnight temperatures have again stiffened slabs and may result in a repeat of Wednesday's conditions.  This is especially true in upper elevation terrain where the snowpack has remained cold.  The hazard will likely be higher above treeline than near the treeline, and steep slopes will be the most probable locations to release.  What continues to remain uncertain is how the rising temperatures will impact the overall likelihood of avalanches.  Most probably, there will be varying windows in time today when slab stiffness and brittleness combine to potentially trigger a release with the added weight of a skier or rider.  Forget about predicting the precise timing of this event, as it will vary spatially and temporarily on both large and small scales.  Instead, focus on conservative decision making, using proper travel protocols, and sticking to simpler and lower angle terrain.

Summarily, we are still dealing with two potential problems that are, in some ways, currently intertwined: the wind slab and persistent slab problems.  And, to confuse things even more, we have the possibility of a third:  wet loose avalanches.  This third problem, (wet loose avalanches), may be on the rise as temperatures increase and the most recent wind affected snow is exposed to radiant conditions.  

Winds have been calm to light for nearly 72 hours, yet the wind slab problem is, in some ways, not totally abating.   Wednesday's slide in the Humphrey's cirque was likely the effect of slabs created by the wind with a newly developed persistent weak layer below.   Still, hollow and firm wind slabs may soften and become more prone to triggering as the day goes on and temperatures warm, especially if these persistent weak layers exist.  Beware of hollow sounding snow and avoid loaded areas in steep terrain.

The persistent slab problem is currently hard to assess and varies significantly across slopes, depending on subtly terrain features and aspects.  Facets and preserved near-surface facets have been found at, near and below the new snow/old snow interface.  Assess steep slopes carefully and utilize proper travel protocols.  These avalanches can release unpredictably and even on tracked and traveled slopes.  If triggered, the consequences, especially in steep and rocky terrain, could result in injury, and/or partial or full burial of a skier or rider.  Yesterday, repeated results of propagation in ECT tests at moderate strength were recorded on a SE slope at the old snow/new snow interface at 12,500 ft.  This observation indicates that the most hazardous persistent slab problem is on this interface and may be more widespread than anticipated.  

As temperatures warm, and as slopes see incoming solar radiation, wet-loose avalanches could possibly develop.  These avalanches will not bury an individual, but they could knock a skier or rider off their feet and over consequential terrain.  Worse yet, it is possible that they could step down and trigger a persistent slab avalanche that might result in a full burial.  If the weather is clear and the temperature increases, look for signs of instability, such as melting snow and roller balls.  These are visual cues that a skier or rider could trigger a small, wet, loose avalanche.

As weather conditions improve post-storm remember to use your own senses and what the snow is telling you to guide your decision making.  The evidence of yesterday demonstrates that there is still a hazard in the forecast zone.   Watch for signs of instability, such as cracking, whumphing and previous avalanches.  Conditions will change rapidly today, and the snowpack is highly variable across aspect, elevation, and terrain.  Play it safe.  Put the odds in your favor by digging test pits before skiing complex terrain to determine the potential reactivity of any weak layers in your present location.

Finally, watch for obstacles buried just below the surface.  A number of upper elevation and south facing slopes that look to hold excellent turns may be hiding rocks and logs just below the surface.  Use pole probe tests to constantly check snow depths and be aware of which sides of slopes may be just 10-30 cm deep.  With all the new snow, some slopes are deceptively shallow, especially after the winds that occurred throughout the storm, which scoured some areas.  

Storm totals from the last cycle are 35" reported by the Arizona Snowbowl at 10,800' and 21" at the Snowslide Canyon SNOTEL with 3.7" of SWE.  Enjoy these last little bits of powder skiing before the spring corn cycle sets in. 

Come join Kachina Peaks Avalanche Center on Saturday, April 6th, at the Agassiz Lodge deck for the Mikee Linville Fundraiser!  All proceeds from this event go to our scholarship fund, which, to date, has resulted in over 29K of scholarship benefits!  For more information on how to get involved, visit kachinapeaks.org.  Many thanks to everyone who made our avalanche courses a success this season and a big thank you to all our participants!