Natural and human triggered avalanches may be possible during this current weather pattern. Significant amounts of new snow and wind transported snow will raise the probability of natural and human triggered avalanches.
Current skiable terrain with sufficient coverage is mostly on wind protected slopes and/or northerly aspects. Year to date snowfall is at 83", with a base of @ 36".
Persistent weak layers have been an issue this year. See AZ snow pit data at snowpilot.org - link also under the snowpack menu. No human triggered avalanches have been reported this season. No significant natural avalanches reported since the small loose-snow avalanches of February 28, 2018. On Monday, March 12th some small loose wet avalanches were reported in Humphrey's Cirque - see photo below.
Near and Above TreelineWith new snow and wind, new wind slabs may form on leeward aspects. With the past week's warm weather, expect to find new melt/freeze crusts on many aspects. Crampons may be helpful in freezing weather where the melt/freeze crust is hardest/thickest. New snow may not bond well to these crusts.
A weak layer of basal facets exists on northerly aspects, and has been reactive in some testing. Also, check for stratification of weak layers in wind slabs on previously loaded slopes.
Below TreelineWith ~36" (94 cm) undisturbed settled snow depth at 10800' (NW aspect), rocks and logs remain primary hazards. Most northerly aspects will have the best coverage with measured depths at 10000' ranging from 22 to 50" (56 cm to 127 cm), while south facing slopes range from no snow to 28" (71 cm) in favored locations near treeline. Melt/freeze crusts have developed on most aspects.
The snow depth is highly variable due to wind transport and sun affect, aspect dependent.
New snow and wind are in the forecast. Should significant precipitation occur, then watch for unstable slab development. Post storm, warm temperatures and sunshine may destabilize newly formed storm and wind slabs.
Stay away from convex pillows of wind-drifted snow on the lee side of ridges and other terrain features. Wind slabs may have a chalky look and feel. Wind slabs can be very hard, and may present a hollow drum like sound as you traverse across slope. Snowpack tests conducted in wind-loaded areas may reveal a wind slab problem in the upper few feet of the snowpack.
Cohesive slabs above weak basal facets are potential areas of instability. Northerly and Easterly slopes will be the main suspects.
Be cautious of previously loaded terrain - old wind slabs on northerly/shaded slopes may have persistent weak bonds.
This problem is not widespread and the probability of triggering a persistent slab is presumably low. However, significant amounts of new snow and wind loading will increase the probability of collapsing persistent weak layers in the older snowpack stratigraphy.
New snow accumulations may approach 12" in favored, high elevation locations. Wind transport will increase the likelihood of storm slabs on leeward ridgeline aspects and localized terrain with cross loading above tree line.
Loose wet activity on northerly slopes near treeline, Monday, March 12. On this day ASB Top Patrol reported 40° F. at 10am. Photo by Josh Langdon.
Mikee Lineville Backcountry Scholarship fundraiser coming up! March 31st, Saturday afternoon on the Agassiz Deck. Live music, raffle, silent auction. Yahoo! Funds go directly to students to help pay for avalanche courses.
Backcountry Permits are required for travel in the Kachina Peaks Wilderness and available at local USFS locations, as well as at the Agassiz Lodge on Saturday and Sunday until 11 a.m.
Last updated on Thursday March 15, 2018 After a week of unsettled weather, which produced 4 inches of snow at 10,800 ft. last weekend, and another 4 inches (at upper mountain elevations) on Thursday, another storm is building for this Saturday afternoon and evening. Weather models have taken their time to agree upon a unified outcome.
Predicted snow loading continues to be a bit of a crapshoot. Recent models seem to favor a wet forecast, with the possibility of 5-12 inches of new snow at and above treeline, but don’t bet your last dollar on this accumulation. Winds out of the southwest will be strongest as the storm approaches, and will blow at optimum velocities to transport snow onto leeward slopes.
Snowfall should taper off by Sunday midday, introducing a warming and drying trend for the first half of the workweek as high pressure ridging develops.
The next possibilities for fresh snowfall will be around Thursday March 22nd with the arrival of another Pacific storm. At the time of publication, it was too far out to predict snow amounts, however, this storm seems on the warmer side so the snowline will probably be above 8,000 feet.
On the evening of March 15th the Inner Basin SNOTEL site (Snowslide) reported a snow depth of 23 inches (58.5 cm) at 9,730 ft and Arizona Snowbowl reported a settled base of 40 inches (101.5 cm) at 10,800 ft. So far this winter 80 inches (203 cm) of snow have fallen at the mid-mountain study site. Since March 8th the SNOTEL temperatures have been mild, ranging between 22° and 50° F. For the same period, the AZ Snowbowl Top Patrol Station (ASTP - elev. 11555 ft) temperatures ranged between 16° and 41 ° F.
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.