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Northern Arizona has seen a week of winter storms to close out 2021 and welcome the New Year. The Snowslide Canyon Snowtel Site reports 36" (91cm) of snow at 9700' and the Arizona Snowbowl has recorded 68" (173cm) this season and a base depth of 42" at 10,800'.
More than half of our current snowpack has been deposited by several separate events over the course of the last week. Avalanche hazards exist in the form of wind slabs and accumulating storm snow.
Based on limited observations, it appears that the new snow seems to be bonding well with the old, though new wind and storm snow affect will increase avalanche potential. Forecast for Saturday, January 1, 55 mph north wind has the potential to strip some areas and load south facing slopes.
Temperatures in the mountains have stayed below freezing, and the strongest winds have been from the southwest transporting snow onto the steeper slopes of the Inner Basin and Humphreys Cirque. Watch for wind loaded pillows or puffy looking slopes and keep an eye out for steeper convex rollovers that can put tension on the snowpack. Coverage has greatly improved, although observers report hitting rocks and logs below the surface.
Settling has been observed around trees, often a sign of increasing stability. Basal facets are present below the level of our rocky substrate and no propagation has been reported in test pits this week. Storm sluffs large enough to impact a backcountry traveler have been observed.
Early season travel conditions exist. Recreationists should remain cautious of obstacles and thin snowpack. If you haven't already done so, take the time to prepare your ski/ride equipment and kit; check your beacon and practice your rescue skills. Winter recreation has arrived.
Near and Above TreelineUse caution in this terrain as early season conditions continue to exist. Above treeline wind slab avalanches may be possible. Plenty of snow is available for transport and with southwest winds observed in the 15-25 mph range, conditions are ideal for small, but reactive wind slabs to develop. Strong winds beginning tomorrow may create an entirely new set of hazards to the backcountry traveler.
Below TreelineBelow treeline avalanches are unlikely. Use caution in the approach and egress through this terrain as rock and logs will continue to present travel challenges, particularly on steeper terrain.
Terrain traps may also be crossloaded and reactive. Test slopes before crossing or entering steep gullies.
Reactive human triggered windslabs are possible on leeward slopes near ridgelines and crossloaded zones along leeward sides of gullies and sub- ridges. Use caution in these areas, particularly when blowing snow creates poor visibility. Do not end up in a hazardous location unintentionally.
Steep slopes may have enough snow at higher elevations to create storm snow avalanches and sluffs. Even small sluffs can carry an individual quickly downslope and possibly over cliffs or into terrain traps.
Please be sure to share observations with through KachinaPeaks.org, we couldn't do it with out you.
For AZ Snowbowl access updates please refer to snowbowl.ski and flagstaffuphill.com. Uphill travel within the Snowbowl ski area boundary is currently closed. The Kachina Peaks wilderness is accessible from the lower parking lots at Snowbowl.
Always carry the 10 essentials and avalanche rescue gear for wintertime wilderness travel. Submit your observations here.
Updated Wednesday December 31
Favorable conditions for snowfall have continued since Christmas with an additional 38“ of snowfall reported at 10,800 feet since Friday December 24. Temperatures have cooled considerably and the snow line has dropped to between 5500 - 6000 feet during the last two waves of precipitation.
Ridge top wind speeds have been strong (20-35 mph) out of the southwest, particularly during periods of heavy snowfall. Wind transported snow has been observed, especially at elevations above 11,000 feet. Although the precipitation has been spread out over several days, a lot of new storm snow and wind loaded slabs have been added to the previously shallow snowpack.
Looking forward, the long wave low pressure system that has ushered in a number embedded storms has moved eastward. In its wake, a cut off cold core low is currently impacting northern Arizona. A powerful north wind and another 5-9” of snow could fall before this disturbance abates. Sunny and breezy weather will characterize the first week of 2022, with cold nights and gradually warming days.
Snowslide SNOTEL reports 36" (91 cm) of snow at 9,730' on Friday, December 31. So far this winter, we have had a total of 68" (173 cm) of snowfall at 10,800' with a 42" (132cm) undisturbed settled base depth reported by Arizona Snowbowl on December 31.
Since December 24, Snowslide SNOTEL low temperatures have ranged between 15°F on December 30 and 21°F on December 27, while highs have ranged from 21°F on December 28 to 26°F on December 26 and 30. For the same time period, ASTP station (11,555') reports a low of 9°F on December 27, 28 and 29 and a high of 24°F on December 30.
The avalanche problem/character describes part of the current avalanche danger. However because we only realease a summary once a week, the current avalanche problem will likely change.
Understanding avalanche problems is essential, because it allows you to determine your approach and strategies to risk treatment. Below are brief descriptions of avalanche problems/characters, and links to detailed information on the problem, formation, patterns, recognition, and avoidance strategies.
Avalanche Problems Explained Also see the North American Danger Scale.
Release of dry unconsolidated snow. These avalanches typically occur within layers of soft snow near the surface of the snowpack. Loose-dry avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs. Loose-dry avalanches can trigger slab avalanches that break into deeper snow layers.
Loose Dry avalanches are usually relatively harmless to people. They can be hazardous if you are caught and carried into or over a terrain trap (e.g. gully, rocks, dense timber, cliff, crevasse) or down a long slope. Avoid traveling in or above terrain traps when Loose Dry avalanches are likely.
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Release of a cohesive layer of snow (a slab) formed by the wind.
Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side.
Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard.
Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features.
They can be avoided by sticking to sheltered or wind-scoured areas.
Release of a cohesive layer of soft to hard snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow.
Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
The best ways to manage the risk from Persistent Slabs is to make conservative terrain choices.
They can be triggered by light loads and weeks after the last storm.
The slabs often propagate in surprising and unpredictable ways.
This makes this problem difficult to predict and manage and requires a wide safety buffer to handle the uncertainty.
Deep Persistent Slab
Release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer, deep in the snowpack or near the ground.
The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
They commonly develop when Persistent Slabs become more deeply buried over time.
Deep Persistent Slabs are destructive and deadly events that can take months to stabilize.
You can trigger them from well down in the avalanche path, and after dozens of tracks have crossed the slope.
Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers.
Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very destructive.
Avoid terrain where and when you suspect Wet Slab avalanche activity. Give yourself a wide safety buffer to handle the uncertainty.
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side.
Cornices range in size from small wind lips of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Cornices can never be trusted and avoiding them is necessary for safe backcountry travel. Stay well back from ridge line areas with cornices. They often overhang the ridge edge can be triggered remotely. Avoid areas underneath cornices. Even small Cornice Fall can trigger a larger avalanche and large Cornice Fall can easily crush a human. Periods of significant temperature warm-up are times to be particularly aware.
Large cornices are generally rare in Arizona, but they have been observed during very snowy winters.
Release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. The are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
Predicting the release of Glide Avalanches is very challenging. Because Glide Avalanches only occur on very specific slopes, safe travel relies on identifying and avoiding those slopes. Glide cracks are a significant indicator, as are recent Glide Avalanches.
Glide avalanches are very uncommon in Arizona.
Snowpack Summary Disclaimer
The summaries on this site were written by Kachina Peaks Avalanche Center Board Members. They are based on a broad spectrum of data collected from weather stations, National Weather Service point forecasts and field observation by qualified individuals.
The summaries are not intended to substitute for good knowledge and decision making skills in avalanche terrain. If you have any doubt of stable conditions, please stay away from avalanche terrain. You can usually find good places to go that are not prone to avalanches, such as on low angle slopes away from avalanche run-out zones. If you have any questions about where to find such places, you should consider further avalanche educational opportunities, such as those listed on our education page.
Snowpack Summary – Format and Limitations Statement
Starting in 2012 Kachina Peaks Avalanche Center (KPAC) has publish a weekly Snowpack Summary on our website.
These summaries are currently issued on Friday afternoons. On occasion, we will give storm updates or warnings of rapidly increasing avalanche hazard at more frequent intervals.
Our objective is to reach weekend recreationist, informing this user group of prevailing conditions, but particularly warning of avalanche hazards whenever they are present.
Many people have asked us why we use the format we do, but do not include a danger rating or a hazard/stability rose as many other avalanche centers do around the west.
The National Avalanche Center (NAC) advises small operations like KPAC, who do not issue daily bulletins to not use danger ratings in our snowpack summaries due to the regular but intermittent nature of their field observations and the length of time between issuance of snowpack summaries.
A primary concern is for how conditions can change in the time between publications, potentially giving the public misleading information. At this point, we simply do not have resources to monitor the snowpack at the level necessary to accurately produce more frequent bulletins.
While we understand the benefits of a danger rating using the North American Danger Scale, we also feel that our format encourages people to dig in a little deeper, and spend some time reading what our forecasters are saying. Although the area that we forecast is relatively small, the variability has proven quite large.
Inner Basin conditions are often surprisingly different from those on the more wind-affected western side on the Peaks.
We hope the information that we provide in summaries helps give you a good overview of what is going on out there, and what avalanche problems you should be attentive to, but if there is any uncertainty, then we encourage you to ask questions via Facebook or email@example.com.