Over the weekend new snow and wind will increase the avalanche hazard. Human triggered storm and wind slab avalanches will be possible and may become likely near and above treeline. Natural avalanches may be possible as wind transports new precipitation above treeline.
Avoid convex pillows of wind-drifted snow, watch for new wind slab development and avoid overhanging cornices that have formed on leeward sides of ridgelines. Cornices on February 25th. Another system may enter the area approximately Wednesday, March 6th and may keep avalanche hazard elevated.
Rapid warming after storms, or rain on snow may lead to wet avalanche activity. Evidence of a smallish wet avalanches were observed on sunny slopes near and below treeline the past few days. We've seen evidence of wet unstable snow on all steep slopes below 9,500'.
Between February 13th and 26th the snowpack roughly doubled. On those dates respectively, we measured ~150cm and ~300cm of snow on an ESE slope at 12,000' near Rustler Peak. Read more about our February recap.
Early February Storm Cycle: Snowslide SNOTEL (9,730') reported 20" of new snow and ~3" of snow water equivalent (SWE) between Feb. 2nd and 6th. This resulted in a large avalanche in Snowslide Canyon on Feb. 5th or 6th. Classification is HS-N-R4D4-O. On Feb. 9th a crown line was observed about 1/2 way down Jay's Slide - a NNW aspect on Fremont. This avalanche likely occurred on Tuesday or Wednesday, February 5 or 6. Estimated classification is U-N-R2D2-U.
St. Valentine's Storm: Heavy dense snow with rain levels near treeline. Snowslide SNOTEL reported 5" of new snow and ~2.5" of SWE between Feb. 14th and 15th. No avalanches observed. New hard/icy crusts in the snowpack.
Presidents Day Weekend Storm: Snowslide SNOTEL reported 9" of new snow and ~<0.5" of SWE between Feb. 17th and 19th. This resulted in small storm and/or wind slab avalanches on Rustler peak. Evidence observed on Feb. 20th. Though not big, these may have been large enough to injure and bury a person. Estimated classification for each is is U-N-R2D1.5-U (35.338, -111.683, ~E aspect). The hard Valentine frozen rain layer was a likely bed surface.
Feb. 21/22 Storm: Snowslide SNOTEL reported 20" of new snow and ~1.4" of SWE between Feb. 20th and 22nd. This resulted in loose snow avalanches triggered by skiers, boarders, and natural small cornice drops. No significant slab avalanches observed.
March 11 update: An old crown line and avalanche debris were discovered in the Telescope Chute of Doyle Peak. The crown was located at ~10,900' at a choke where the path briefly narrows and steepens. Avalanche debris and small broken trees were found at ~10,400’. This avalanche likely happened during the Feb. 21/22 storm.
Near and Above TreelineWatch for new wind slab development and growing cornices on leeward slopes. Expect to find wind scoured zones and hard icy snow above treeline - especially on south , southwest, west and northwest slopes. Crampons and ice axes will help prevent falls on steep icy slopes.
Sunshine after storms may destabilize southerly and sunny slopes.
Below TreelineWatch for rain on snow events, and warm temperatures destabilizing the snowpack.
Tree wells are getting deep and tree well immersion suffocation is a real possibility. Coverage is good on most slopes above 9,500', with plenty of safer low angle (<30°) touring.
New snow slabs and wind slabs will be your primary problem near and above treeline this weekend and next week.
Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Avoid slabs and convex pillows of wind-drifted snow on lee and cross-loaded terrain features.
Forecast calls for new snow and southwest and west winds this weekend, so watch for northeast and easterly wind slab formation. Also, chutes and gullies on other aspects may cross load.
Keep an eye on the ASBTP weather station. Readings between 15 and 35 mph indicate the potential for snow transport and formation of wind slabs. Look for various links under the weather menu above. Note that this station may get rimed during storms and report erroneously.
Waiting at least 48 hours after wind events will decrease your chances of finding unstable storm/wind slabs.
Avoid standing on overhung cornices, as they may collapse unpredictably and send you downslope. They can sometimes break far back on flat ridge-top terrain. Sunny warm weather can naturally release cornices.
Evidence of smallish wet slab avalanches were observed this week on southerly slopes below treeline. Current trend is towards cool and cloudy weather, but when warm weather returns, watch for loose wet and wet slab avalanche potential - primarily on steep southerly and westerly slopes above 10,000'. This could also become a problem on all steep aspects at elevations below 10,000 feet. Rain on snow will destabilize the snowpack on any aspect or elevation.
During warm weather, surface snow will become saturated with water. Deteriorating riding conditions (sticky slush) and rollerballs are an indication that you should move to a colder slope.
Even when things appear stable, there's always some uncertainty. Therefore don't expose all or most of the group to avalanche terrain. This group should spread out more. Feb. 26 J. Langdon photo.
This north-northeast face of Fremont Peak had ski tracks on Wednesday, Feb. 27th. Two days later the tracks were covered by new snow blown in from southwest winds. Friday, March 1st, 2019 photo.
On Thursday, February 28th a fracture was observed in Telescope Chute, a northeast aspect of Doyle Peak. This appears to be a glide crack or an old avalanche crown. March 11 update: We confirmed that this was a crown line. See Overall section.
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.
Weather update Friday March 1st. During the past week we have seen a gradual warming trend, high clouds, but no precipitation. By the time of this report, Temperatures have returned to near normal with daytime highs in the 30s at treeline. In the aftermath of last week’s mega storm, winds out of the north and northwest were observed Saturday February 23rd and to a lesser degree on Sunday and into the workweek. On Saturday Feb. 23rd, wind speeds ranged from 15-30 mph with gust in the 40 mph range out of the north and northwest. Breezy conditions returned on Thursday Feb. 28th and Friday Mar. 1st. These were in the 20+ mph range with stronger gusts out of the west and southwest.
During the upcoming weekend, another low pressure system will pass through. Current forecast is for 10 to 18" of snow near treeline, and a snow/rain line near 8000'. This storm will be accompanied by breezy conditions out of the southwest. During the following workweek, the weather will return to near normal temperatures and breezy days. Another storm my enter the area around mid-week, but it's too early to accurately predict anything about timing, intensity or storm track.
On Friday, March 1st, the Inner Basin SNOTEL site (Snowslide) reported a snow depth of 63” (160cm) at 9,730'. Arizona Snowbowl reported a settled base of 98” (249 cm) at 10,800'. So far this winter, 278" (706 cm) of snow has fallen at the mid-mountain study site. Since February 23rd, SNOTEL temperatures have ranged between 8° F on February 24th, and 46° F on March 1st. For the same period, ASBTP (11,555') reported temperatures between 1.6° F on Feb. 23rd, and 35.7° F on March 1st.
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.