Natural avalanches are currently unlikely, while human triggered avalanches are possible in isolated pockets of recently loaded slopes. Skiers and snowboarders should take extra care in assessing the conditions over the next 72 hours; as subtle aspect changes, elevation changes, and terrain features can be the difference between extremely hard packed old snow and newly formed reactive wind slabs.
All slopes should be met with a critical eye, looking for possible signs of instability and windslabs. Wind direction and speeds can drastically change as a response to local terrain features. However, moderately sheltered north and northwest slopes at and near treeline likely harbor the highest risk of new reactive wind slabs. Although these avalanches would likely be small, they can still be dangerous (i.e., knocking a person off their feet in extreme terrain, carrying the individual into terrain traps, across exposed rocks, or into trees).
Last weekend’s weather was dominated by warm and mild conditions. On Tuesday an approaching low-pressure system drastically decreased temperatures and delivered a few inches of snow across the peaks and the surrounding area. In total, this storm delivered 5 inches of new snow at 10,800’ at the Arizona Snowbowl and 7 inches of new accumulation in Snowslide at the SNOTEL study site (9,370’).
Unfortunately, this storm was also accompanied with post frontal north easterly and easterly winds that likely exceeded 50+ MPH above treeline, sublimating much of the new snow on windward and exposed slopes.
Early season conditions persist and recreationists should remain cautious of obvious and partially buried obstacles.
Note that we have changed the format of our elevation sections to Near and Above Treeline (~10,800' and above) and Below Treeline (~below 10,800’). We did this for two reasons: first to be specific; and two, most of the San Francisco Peaks avalanche starting-zones lie above 10,800 feet. In general, the weather is similar between 10,800' and the highest point of 12,633 feet.
Near and Above Treeline (~10,800' and above)Wind cycles continued this week and sublimation of high elevation snow persists. While no signs of instability were noted prior to the recent storm, pockets of freshly loaded wind slab will likely be reactive and skiers and riders could trigger small slides in these drifted pockets.
Crampons and ice axes may be needed at and above treeline where snow persists, with rocky conditions dominating the remaining terrain. South facing terrain may be entering a melt freeze cycle with warmer temperatures this week.
Below Treeline (~below 10,800')Thin coverage, rocks, and logs will make approaches and egresses challenging, particularly below 10,500' on southern aspects. Northern aspects still have acceptable coverage down to ~9,000 feet.
With the recent snowfall and post frontal winds, there is a possibility of triggering wind slabs in cross-loaded pockets and along ridgelines. Although, high winds likely sublimated and stripped much of the new snow at higher elevations (above treeline), protected areas and lower elevation pockets likely harbor the highest risk of wind slab formation.
Caution is advised when skiing wind pocketed terrain in areas where wind was able to deposit and form wind slabs.
Small reactive slab on a northwest face of North Core after the late January storm and post frontal winds. Conditions prior to this small release were similar to current conditions (1/24/22).
Always carry the 10 essentials and avalanche rescue gear for wintertime wilderness travel. Submit your observations here.
For AZ Snowbowl uphill access updates please refer to snowbowl.ski and flagstaffuphill.com. The Kachina Peaks wilderness is accessible from the lower parking lots at Snowbowl.
A free Avalanche Awareness Clinic will be held at SMR (Snow Mountain River), next Thursday, February 24, 6:30 p.m. Check in with SMR to register for the event!
Updated Friday February 18
Last week warm weather was replaced by a pattern breakdown allowing an interacting pair of relatively moisture deprived low pressure troughs to track through northern Arizona. The result was more wind, cooler temperatures and the first recorded snowfall on San Francisco Peaks since January 23, after twenty-five days of drought. Arizona Snowbowl reported 5” of new snow on Thursday February 17. Strong post frontal winds out of the northeast on Thursday gusted to 49 mph at 11,500 feet.
For the weekend, the Pacific high pressure system appears to rebuild, so a gradual warm up, with dry weather forecast to return. However, this will be short-lived, as President’s Day ushers in a long wave trough and good chances of more snow and winter weather. This storm may last through the middle of next week. The collective hope for new snow and the salvation of winter may become a reality over the next seven days.
Snowslide SNOTEL reports 38” (99 cm) of snow at 9,730' on Friday, February 17. So far this winter, we have had a total of 91” (231 cm) of snowfall at 10,800' with a 50" (126 cm) undisturbed settled base depth reported by Arizona Snowbowl on February 18.
Since February 4, Snowslide SNOTEL low temperatures have ranged between 10°F on February 17 and 28°F on February 11, while highs have ranged from 35°F on February 16 to 51° F on February 14. For the same time period, ASTP station (11,555') reports a low of 4°F on February 17 and a high of 44°F on February 11.
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 firstname.lastname@example.org.