Natural slab avalanches are currently unlikely. Human triggered avalanches are possible near and above treeline in isolated pockets on recently wind loaded slopes and steep gullies, though the likelihood of significant avalanche activity is minimal.
Near record breaking high temperatures are forecasted for Friday February 11 and through the weekend, and could initiate small, loose wet snow avalanches on warm south and southwest facing slopes, particularly near radiation absorbing rock outcrops and at lower elevation.
The prolonged drought and cool nighttime temperatures over the past two weeks have caused a variety of facets to form on different aspects and at different elevations. Persistent weak layers are maturing. Although these present no hazard right now, they could furnish the ingredients for increased instability following our next significant snow storm or wind loading event. With such an occurrence in the realm of possibility mid next week, instability could rise sooner, rather than later.
Snow surface conditions are highly variable. Some of the larger slopes, particularly in the inner basin, remain skiable. Other aspects include breakable crust, wind buff, and even some soft recycled powder in cool sheltered locations. Finding quality turns has been challenging.
It has now been 16 days since the last recorded snowfall.
Unfortunately, early season conditions persist and recreationists should remain cautious of obvious and partially buried obstacles.Only one very small (R1D1) avalanche has been recorded this season, occurring January 23rd.
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 last week combined with warmer temperatures. Sublimation of high elevation snowpack persists. While no signs of instability have been noted, pockets of freshly loaded wind slab can not be ruled out, skiers and riders could still 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.
Conditions at treeline and in sheltered areas remain better than expected due to cool nights and radiation recrystallization (recycled powder).
Small, loose wet avalanches may become possible with the heat wave predicted this weekend and early in the workweek.
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 ~9000 feet.
There is a possibility of triggering small wind slabs in cross-loaded pockets near and above treeline. Caution is advised when skiing steep wind pocketed terrain in these locations.
Although snow available for transport is minimal, moderate to strong winds over the last week have have been theoretically optimal for moving snow via the saltation process. A few isolated northern and eastern aspects, primarily in couloirs and on the sides of ridges, may have received some loading.
Cool sheltered glades provide good skiing on recycled powder. Photo by Kyle Johnson
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.
Updated Friday February 11
Last week was dry and warm with some breezy to windy interludes. Gusts of 64 mph were recorded on February 6 at 11,500 feet, and near 50 mph gusts every day since. Midweek, high temperatures rose above seasonal norms breaking freezing at 11,550 feet. Close to record breaking heat is predicted for the weekend and continuing into the workweek.
Looking forward, following the heat wave, expect a pattern change to unsettled weather. An upper level low is predicted to develop and approach the Southwest. At the moment, model agreement is still scattered, resulting in uncertainty of the storm’s specific track and impact. The best chances for precipitation appear to be Wednesday February 16.
Snowslide SNOTEL reports 34” (86 cm) of snow at 9,730' on Friday, February 11. So far this winter, we have had a total of 86” (218 cm) of snowfall at 10,800' with a 47" (119 cm) undisturbed settled base depth reported by Arizona Snowbowl on February 11.
Since February 4, Snowslide SNOTEL low temperatures have ranged between 9°F on February 5 to 19°F on February 8, while highs have ranged from 32°F on February 6 to 45° F on February 10. For the same time period, ASTP station (11,555') reports a low of 17°F on February 6 and a high of 42°F on February 5.
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.