A winter storm warning is in effect until 6am Thursday morning, March 19th. The likelihood of natural and human triggered slab avalanches is increasing. As of 4pm Snowslide Snotel (9730') reports 8" of new snow with 1.2" of snow water equivalent. ASBTP station is not reporting, but Little Spruce station (9379') reports moderate to strong southwesterly winds. More snow and wind will continue through tomorrow.
To help prevent the spread of COVID-19, Arizona Snowbowl has suspended all operations until further notice. Snowbowl road is currently closed, and backcountry access points will require a very long hike, e.g. Lockett Meadow road. Be prepared and pay attention to your energy levels, and your partner's energy levels. With the ski area closed, rescue response will be slow. Make conservative decisions and keep your risk tolerance low, for yourself and the community - now is not a good time to visit a hospital which may be overwhelmed due to COVID-19.
Recent pits reveal that the avalanche triggered by ski patrol may have involved an isolated snowpack structure, but KPAC encourages backcountry users to analyze the March 11th rain-crust (and above snow) on near-treeline slopes - especially northerly slopes just below ridgelines.
Click Read More for a few things to be aware of during this storm cycle.
- 90% of human triggered avalanches happen during or within 24 hours of snowfall. Waiting 24 hours before traveling on or under steep (>30°) slopes will decrease your likelihood of triggering an avalanche - Venture into this new snow with an "assessment" mindset by selecting conservative terrain in which to gather information - Check the bonding and reactivity of new storm and wind slabs - Look for signs of recent avalanches - Watch for instabilities like cracks shooting out from your skis or board as you skin or ride in fresh snow - Listen for collapses (whomping) underfoot - Post storm sunny/warm weather may destabilize new slabs (spring equinox is March 19th) - Make good decisions upon your observations - The extended forecast suggest even more unsettled weather next week - keep your guard elevated.
Near and Above TreelineOn March 14, Saturday morning, using explosives in a closed area, Az Snowbowl Ski Patrol triggered an avalanche. NW slope near 11,800ft. The crown was 2-4' deep. It ran approximately 800' and was about 75' wide. The debris pile was ~4' deep where it stopped above the spur catwalk. This was a wind slab that failed on needles resting on the March 11 rain crust. Recent pits reveal that this may have been an isolated snowpack structure, but KPAC encourages backcountry users to analyze the March 11th rain-crust (and above layers) on near-treeline slopes - especially where you find wind loading.
Approach ridges and leeward terrain with caution. Wind can deposit snow 10 times more rapidly than snow falling from the sky multiplying the load on the snowpack. Be very suspicious of any steep slope with recent deposits of wind drifted snow.
Even though there is new snow, there may still be areas of exposed ice and hard snow. If you plan to to go above treeline, take an ice axe and crampons as a precaution. Some windward areas of the peaks were stripped of snow during the February high-wind events, while other areas have retained a 1-2 meter snow depth.
Below TreelineNew snow will hide previously exposed rocks and logs. Coverage has improved, but our mid-winter drought made egress from the backcountry more difficult as many standard routes are a bit burned out, requiring more hiking. Ski area closures and road closures requires even more hiking. Plan accordingly.
Northerly, Northeasterly and Easterly slopes may develop wind slabs. Winds may also cross load other aspects.
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 are usually confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas.
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.
On March 14, Saturday morning, using explosives in a closed area, AZ Snowbowl Ski Patrol triggered an avalanche. Chad Trujillo, 3/14.
Closer view of the 3/14 explosives triggered avalanche. Ken Galinski, 3/14.
Always carry the 10 essentials and avalanche rescue gear for wintertime wilderness travel. Submit your observations here. You may save a life!
Weather update Wednesday March 18
We are in the midst of a potent winter storm. a winter storm warning was issued for elevations above 6000’ for Wednesday night March 18th. Between Wednesday afternoon and Friday the 20th, 18"-26" of snow is predicted to fall at treeline. Windy conditions will accompany precipitation with velocities in the 20 mph range, and gusts in the mid 30 mph range. Starting out of the south, winds will shift to the southwest and west as the storm progresses.
Below numbers last updated on March 13th. Arizona Snowbowl reported a 64" ( 163cm) base at 10,800 feet. Snowslide SNOTEL is reporting a questionable depth of 51" (130cm) at 9,730 feet. So far this winter, 182" (462 cm) of snowfall has been reported at 10,800 feet.
Since Friday March 6th, SNOTEL temperatures have ranged between 49°F on March 12th and 24°F on March 9th. ASBTP station (11,555 ft) reported a low of 15°F on March 9th and a high of 40°F on March 6th.
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.
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.
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.