This summary is generously sponsored by Babbitt's Backcountry Outfitters. A family owned, local outdoor gear shop in the heart of historic downtown Flagstaff, Arizona
Winds and snow are actively loading northerly slopes near and above treeline. Human triggered avalanches will be possible, and may become likely where larger, cohesive wind slabs form. With a storm system moving through today and tonight, expect avalanche hazard to stay elevated over the weekend.
The January 22-26 storm cycle resulted in 63" of new snow at 10, 800', and 33.2" at the Flagstaff Airport, ranking it 15th among top Flagstaff accumulation events. Today a quick moving system is forecasted to result in 7-14" of new snow near treeline along with strong southerly and westerly winds. Expect this system to exit our area by Saturday morning. By Sunday night winds are expected to become moderate from the north.
Though it's almost February, early season conditions exist. Ski's and snowboards have been broken on rocks this week. Kneepads, helmets and treading gently are recommended.
AZ Snowbowl reports 62" base. No natural avalanches reported this season, and no human triggered avalanches reported since January 25th.
When is the last time you practiced your avalanche rescue skills? How about your partner? Chapter one of your season plan and goals should start with rescue practice that adequately justifies the rest of your season.
There may be a lingering persistent slab instabilities where the most resent snow accumulated over weak early season snow. We have no direct evidence of this problem, nor have any avalanches associated with this issue been observed. Therefore, the persistent slab problem has been removed from the problems section. Note that there is a degree of uncertainty about this issue, and a lack of focused assessment in the terrain where such a problem may exist. If it is indeed an issue, then it will likely be limited to above/near treeline northerly aspects, particularly smoother cindered slopes with few anchors.
Backcountry travelers should carefully assess any slope steeper than 30°, as well as any slope connected to steeper (>30°) slopes above. Venture into the new snow with an "assessment" mindset by selecting conservative terrain. Assess the bonding and reactivity of new storm and wind slabs.
Near and Above TreelineWith current winds and the new storm, watch for reactive wind slabs on NW, N, NE and E slopes. By Sunday morning a switch in wind may result in reactive slabs on ~southerly slopes. Easterly and northerly slopes have the best coverage. They may also have the most reactive wind slabs.
There may be thin spots so watch for log strikes in rocky and forested terrain.
Below TreelineExpect rock and log strikes in rocky and forested terrain. With the current storm system, watch for new storm slab development in steep sheltered terrain.
With current winds and the new storm, watch for reactive wind slabs on NW, N, NE and E slopes, near and above treeline. By Sunday morning a switch in wind may result in reactive slabs on ~southerly slopes.
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Weather updated Friday, January 29, 2021
The January 22-26 storm cycle resulted in 33.2" of new snow at the Flagstaff Airport, ranking it 15th among top Flagstaff accumulation events. Today, a quick moving system is forecasted to result in 7-14" of new snow near treeline along with strong southerly and westerly winds. Expect this system to exit our area by Saturday morning. By Sunday night winds are expected to become moderate from the north.
Expect high pressure and fair weather for the weekend and early next week, along with near normal daytime temperatures on Sunday and Monday. The next storm system is forecast to arrive late Tuesday or Wednesday. At this time there is uncertainty with regards to winter weather impacts.
Snowslide SNOTEL reports 44" of snow at 9,730' on Friday, January 29. Since Friday, January 22 Snowslide SNOTEL low temperatures have ranged between -1°F on January 26, to 26°F on January 28 while highs have ranged from t 15°F on January 26 to 40°F on January 28. For the same period, ASBTP (11,555') reported a minimum of -1°F on January 26 and a maximum temperature of 31°F on January 28.
So far this winter we have had a total of 99" of snowfall at 10,800 feet, with a 62" undisturbed settled base depth reported by Arizona Snowbowl on January 29.
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.