The spring melt/freeze (m/f) cycle continued this week, with a bit more freeze than melt the last few days. Today 3 to 7" of snow is forecasted for treeline, where new storm/wind slab development will be possible. Light winds and accumulation, combined with post storm m/f action, may render any new slab problems non-existent or short lived. But do pay attention to snowfall amounts, wind, and bonding of new/old snow. New slabs may have a hard time bonding to cold frozen m/f crusts which have formed on all aspects. Some upper elevations ( approx. >11,000') may have a thin layer (<1") of faceted April 10th snow, possibly creating a weak layer under new accumulations.
Human triggered storm/wind slab avalanches may be possible with the April 12th storm. With limited accumulation, these avalanches will likely be small. Another storm near the middle of next week may produce more storm/wind slab problems. Wet avalanches are unlikely near and above treeline during the mornings. As the days heat up, natural and human triggered wet avalanches will be possible. New snow will saturate first, possibly producing avalanches that slide on frozen m/f crusts.
This week marks our first snow accumulation since March 22nd. No significant slab avalanches reported since February. Wet avalanche debris were observed recently on a north aspect of Doyle Peak. See below photo.
Read more about springtime touring strategies.
Backcountry conditions are dynamic, and can change rapidly, especially in spring. Pay attention to changes in snowfall, wind and temperature and how those changes affect the snowpack. Spring skiing entails monitoring overnight temperatures and what elevation freezing occurs and for how long. Saturated deep slush is indicative of wet slide hazard.
Near and Above TreelineWith wind and snow in the forecast, watch for new storm/wind slab development. New snow will be the first to saturate and possibly produce wet avalanches when the sun returns.
As the days heat up, natural and human triggered wet avalanches will be possible on southern aspects and any slopes receiving strong solar input. Expect to find wind scoured zones and hard icy snow above treeline. Crampons and ice axes will help prevent falls on steep icy slopes.
Below TreelineCoverage is good on most slopes above 10,000', with plenty of safer low angle (<30°) touring. Southerly and sunny slopes are rapidly losing snow as we push into spring.
When the warm spring weather returns, wet avalanches may be possible on steeper isolated slopes where the snowpack has become saturated by a combination of sunshine and above freezing overnight temperatures. Watch for saturated, and deep slushy snow around terrain traps and any slope steeper than 30°.
Wet avalanche hazard is unpredictable. Warm temperatures and consistent nights with above freezing temperatures are warning signs of an unstable wet snowpack.
With wind and snow in the forecast, watch for new storm/wind slab development near and above treeline. When the sun and warmth return, new slabs will be the first to saturate and possibly produce wet avalanches.
As the days heat up, watch for loose wet and larger wet slab avalanche potential. Wet avalanche debris were observed recently on a north aspect of Doyle Peak, near 10,500'. See below photo.
"Heating happens fast this time of year, with snow changing in a matter of minutes. Watch for the usual signs of wet instability including roller balls, point releases, and damp, heavy, loose snow. You’ll need to constantly monitor snow surface conditions […] Keep in mind what you’ll be traveling under as you exit the mountains [during the heat of the day]" -Utah Avalanche Center
Watch out for above freezing overnight temperatures leading to saturated and unstable snow on any steep aspect below ~10,000'.
During warm weather, surface snow will become saturated with water. Deteriorating riding conditions (thick and sticky slush) and rollerballs are an indication that you should move to a colder slope or head home.
Cornices have formed along ridgelines and cross loaded features. Stay away from the edges of tall and/or overhung cornices, as these may collapse unexpectedly and break further back than you may expect. See image of cornices in the April 5th summary.
Avalanche debris near 10,500' on north aspect of Doyle Peak, April 09, 2019. This wet loose avalanche likely released on April 8th, when treeline temperatures pushed 50°F.
Logging began along the first 1/4 mile of Freidlein Prairie Road (FR-522). Loggers will plow that stretch of road and need gate access. This is part of the Chimney Springs thinning project.
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 8:30 -11:30.
The past week started out feeling like summer with temperatures 5 to 8 degrees above average, however, bliss was quickly followed by a return to winter with strong winds and a sharp cool down. On Tuesday through Thursday strong winds out of the southwest shifted to the northwest with the passing of a major cold low pressure system to our north. Temperatures in the teens and wind chill below 0°F were recorded. Snow showers were observed, but only 1" accumulated at upper elevations.
On Friday and Saturday April 12 and 13, a significant cold front will brush by to the north, potentially delivering 3-6 inches of new snow and a continuation of windy, cold, unsettled weather. Following this event is a slight warming trend, however, the weather will remain unsettled early in the workweek, with cool nights, warmer days and gusty afternoons. A possibility of snow showers is foretasted through Tuesday April 16. Snow accumulation will probably be light, but storm trajectory and strength are uncertain at the time of publication.
On Friday, April 12th the Inner Basin SNOTEL site (Snowslide) reported a snow depth of 48” (121 cm) at 9,730 feet. Arizona Snowbowl reported a settled base of 88” (224 cm) at 10,800 feet. So far this winter, 328” (833 cm) of snow has fallen at the mid-mountain study site. Since April 5th, SNOTEL temperatures have ranged between 18°F on April 11, and 62°F on April 8. At ASBTP (11,555'), temperatures reported over the last week were between 12°F on April 11, and 50°F on April 8.
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.