In general, slab avalanches are unlikely on the San Francisco Peaks over Valentine's/President's day weekend. Loose wet avalanches will be possible during the warmer hours this weekend. There exists the remote possibility of finding some recently formed and reactive wind slabs in isolated terrain. With only minor amounts of snow available for transport, wind slabs may be small and likely confined to steep and extreme terrain near/above treeline and near ridgetops. Keep in mind that even small avalanches can have grave consequences in extreme terrain.
The last two storms have tracked just north or south of us, keeping things windy, but resulting in very little precipitation. The next chance of precipitation and wind is forecasted for Sunday/Monday, although moisture associated with the trough will likely remain north of Flagstaff. Any precipitation and additional winds this storm delivers will likely increase avalanche hazard. Until then, spring skiing and riding conditions are likely to persist on the San Francisco peaks, particularly on south facing slopes.
Overall, the snowpack has a complex and poor structure, moderate to good strength, and low reactivity. No new slab avalanches have been reported since the Christmas storm cycle.
Near and Above TreelineIce axe and crampons are strongly recommended as surface conditions can be very firm depending on the time of day and temperature. Always be cautious of wind slab formation on steep, leeward slopes. Observe for local signs of wind stripping and subsequent loading on leeward aspects wherever you travel above treeline. Where wind has not scoured snow, depths remain at 1-2 meters.
Below TreelineWith a decrease in elevation comes a decrease in snow depth. Obstacles become the main hazard below 9500 ft but are present on all aspects at all elevations. Sunny and southerly slopes below 9500 ft are getting difficult to navigate with skis. Always expect the unexpected. If any new snow falls next week then obstacles may become covered and hidden just below the surface. Ski and snowboard with care after new snow.
When daytime temperatures warm, stability on sunny aspects may deteriorate. Time your corn snow harvest appropriately. One relatively small wet slough was reported on Saturday, Feb. 1st, on a sunny southeasterly slope.
For springtime corn turns, timing is key to avoid hazards associated with a warming snowpack. With weekend temperatures >40°F forecast at 10,000 ft, avoid steep, sun exposed terrain as stability deteriorates during the heat of the day.
With only minor amounts of snow available for transport, wind slabs will be small and likely confined to steep and extreme terrain near/above treeline and near ridgetops. Keep in mind that even small avalanches can have grave consequences in extreme terrain.
Wind Slabs can be very hard, and may present a hollow drum like sound as you traverse across slope. Hard slabs are most prone to human triggering where they are thin/weak, and therefore, more susceptible to failure under a person's weight.
View looking up Core Ridge. Snowslide canyon on viewer left and the edge of Humphreys Cirque on viewer right. Feb. 9th photo by Troy Marino.
This lone cornice was observed Feb. 13th at the top of Heck Yeah Chute. Cornices tend to destabilize in warm weather, and cornice collapses can trigger larger avalanches.
Always carry the 10 essentials and avalanche rescue gear for wintertime wilderness travel. Practice with your avalanche rescue gear. There is still space available in our avalanche courses.
Submit your observations here. You may save a life! The link to this form is now on our home page and snowpack menu.
Unsettled weather early last week sent the brunt of precipitation to eastern Arizona and New Mexico. Locally a net accumulation of only two inches of new snow was reported at 10,800 feet. Strong storm and post-storm rap-around winds blew out of the east and northeast Tuesday, moving what little new snow had fallen onto leeward aspects. Cool crisp days and a gradual warming trend followed later in the week. Winds subsided and warm weather prevailed leading into the weekend. Breezes will kick up as a dry short wave passes on Friday and Saturday.
The next chance of significant precipitation is currently uncertain. A short wave trough out of the northwest, previously predicted to arrive on President’s Day, now appears to be shifting to our north, bringing only cooler temperatures and more breezy conditions. Normal to slightly below normal temperatures will linger into the workweek.
Arizona Snowbowl reported a 54" (137 cm) base at 10,800 feet. Snowslide SNOTEL reports a 45" (114 cm) snow depth. So far this winter, we have had 147" (373 cm) of snowfall at 10,800 feet.
Since February 7th, SNOTEL temperatures have ranged between 47° F on February 7th and 11° F on February 11th. ASBTP station (11,555 ft) reported a low of 7° F on February 11th and a high of 38° F on February 7th.
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.