As we head into the second half of the season, we may start to see danger ratings dropping in parts of the interior. But before we start making big plans, we should take a moment to reflect on the current state of the snowpack and the mindset needed for a safe second half of the season.

Deep persistent slab avalanches continue to be our biggest concern throughout the interior. These two avalanches failed naturally in the Purcells, near Golden on Tuesday, January 24. They failed on a layer of facets near the base of the snowpack. MIN photo from A SHERRIFF

A deep persistent weakness exists throughout much of the interior. It has been popping up in different areas at different times and has been unpredictable, which makes forecasting for it difficult. Most recently, we have seen very large avalanches failing near the ground in the mountains around Valemount and Golden. Earlier in the month, we saw the same type of avalanches around Revelstoke and Nelson. We expect the weakness is still lingering through most of the interior and could produce very large and destructive avalanches with the right trigger. The layer seems most problematic at upper treeline and lower alpine elevations. We’ve also seen many reports of remote triggering of this layer, which means you might be able to trigger the layer from below the slope, from a ridge above the slope, or from an adjacent slope. This means you should be giving large, suspect slopes a wider margin of error than normal and be constantly vigilant about what is above you. 

A layer of surface hoar from early January also continues to produce large and unpredictable avalanches. This layer is typically down 40-90 cm through most of the interior, making it prime to be triggered by the weight of a rider. This layer has been most reactive around treeline and the upper parts of below treeline elevations. 

For a refresher on the deep persistent problem, check out the blog from our Senior Forecaster Mike Conlan from early January called “The Persisting Problem”. 

A layer of surface hoar from early January remains reactive and resulted in this persistent slab avalanche in Rogers Pass on Wednesday, January 25. This layer continues to produce large, human-triggered avalanches throughout the interior. MIN Photo from SONDRE100.

Strategic mindset is a term that is now well established amongst avalanche professionals in Canada. The original concept was established by Roger Atkins in a 2014 paper called “Yin, Yang, and You”. It establishes the following seven strategic mindsets: initial assessment, stepping out, status quo, stepping back, entrenchment, open season, and spring diurnal. 

Two of the most common mindsets being used by professionals at the moment are stepping back and entrenchment. While we often associate the term entrenchment with the patience needed during big storms, the term has been used lately when referring to the approach to our deep persistent slab problem. Many professionals stepped back a few weeks ago when the large avalanches began to occur and have been entrenched since then. This means they are skiing the same runs over and over and avoiding pushing out into terrain that has not been used this season. They are sticking to low angle slopes and tight trees where they are certain the problem doesn’t exist. 

The original strategic mindset diagram. The common thing with stepping back and entrenchment is that they both lead professionals to stick to safe terrain. Image source: Yin, Yang, and You, Roger Atkins, ISSW 2014.

In our forecasts, we often use the terms like ‘conservative’ or ‘patient’ mindset. We use these to mean people should to stick to simple, safe terrain and not be lured into bigger terrain features by boredom or ambition. It takes a lot of discipline to spend the whole season with simple objectives, but this is the attitude that professionals are using at the moment. It is the only way to ensure you don’t push yourself too far and end up triggering a large, unexpected avalanche. 

The snowpack is highly variable throughout the interior, which makes it unpredictable. Unless something drastic changes in the snowpack, this could continue for the rest of the season in parts of the interior. One of our main concerns about this situation is that we can’t say exactly where and exactly when the deep layers will be reactive. This uncertainty is why we are continuing to issue warnings about the snowpack for most of the interior in our forecasts and communications.

First consider your mindset when planning your trip. Reassess your mindset during the day and ensure your travel habits are aligned with your mindset. Finally, assess if your mindset was appropriate while you are reflecting on your day. 

Over time, we may start to see the danger ratings drop to moderate for some of the interior. However, it is important to remember that this does not mean there is no danger. The persistent and deep persistent slab problems are expected to continue to be a major concern, even if we start to see the frequency of large avalanche events decreasing. 

Forecasting for a deep persistent problem is complex, because it doesn’t fit nicely into the definition of either moderate or considerable danger. For example, the likelihood of triggering an avalanche might fit best into the moderate definition as the time passes, however the size and unpredictability of that avalanche fits more comfortably into the considerable definition. As forecasters and recreationists, we have to decide how much weight each part of the definition carries. Personally, I weight the travel advice section much higher than the likelihood section. I would also weight very large avalanches in isolated areas much higher than small avalanches in specific areas. With that in mind, I almost always lean more towards considerable than moderate in a situation like the example shown below. This is the classic low probability/high consequence problem associated with a deep persistent slab problem. 

A hypothetical breakdown of Moderate and Considerable danger rating for the current deep persistent slab problem. How much weight would you put on each part of the definitions? 

For more details on moderate hazard, check out this great blog post Managing Moderate from our Senior Forecaster, Grant Helgeson, who provides the following advice: 

Spooky moderate means slopes should be presumed guilty until proven innocent. 

Consider choosing terrain where the consequences of your snowpack assessment being wrong will promote a survivable outcome.

An extra margin of error is needed if we are experiencing changes in temperature.

Few Instability Clues Don’t Mean Stability

One of the hardest things with a deep persistent slab problem is a lack of clues. When we provide advice on managing storm-related problems near the surface of the snowpack, we often advise people to watch for signs of instability like whumpfing and cracking, signs of wind loading, and observations of recent avalanche activity. These are all strong signs that the snowpack is unstable.

With a deep persistent problem, there are typically no obvious clues until it’s too late. The first sign of instability could be a large and destructive avalanche. This makes it very difficult to assess the problem in your local riding area. Bear in mind as you travel that a lack of clues does not mean a deep instability is not present in the area. 

With a deep persistent slab problem, the first sign of an instability could be a large and destructive avalanche. Because the layer is so deep, there may be no clues that an instability exists until it is too late. MIN photo from MLDUQ

One of our biggest concerns for the coming weeks is that clear weather may motivate people to push into terrain that was previously unappealing in poor weather. The temptation might be strong, but we are cautioning people against pushing into untracked or unfamiliar terrain. Big, untracked slopes are one of the most likely places we would expect a deep persistent slab avalanche to occur. One of the most common themes amongst professionals when they talk about managing the current snowpack is the use of familiar terrain. They are sticking to previously skied terrain which they know is well tracked and tested. This approach can also be applied by recreationsists by selecting busy areas that get tracked out everytime it snows. 

Large, untracked slopes may be alluring during periods of clear weather, but resist the temptation to push into bigger terrain, especially where a thin alpine snowpack may make it easier to trigger a deep instability. Photo: Ryan Buhler

Since we will likely be dealing with the deep persistent slab problem for the rest of the season in parts of the interior, here are some tips for managing terrain and keeping a disciplined mindset:

Stick to simple, low angle terrain. Resist the temptation to push into bigger and steeper terrain. 

Remember that large, destructive avalanches can still occur with a moderate danger rating.

Choose terrain that promotes a survivable outcome if an avalanche occurs. Consider: if the slope produces an avalanche while you are on it, what would the worst case result be? 

Use a conservative mindset even if you are not seeing clues of instability. Clues of a deep instability may not exist until it is too late. 

Plan to maintain a conservative mindset, even after evidence seems to indicate these instabilities are no longer a concern.

Be willing to postpone plans for big, committed objectives and accept that they may need to wait for another year. 

The possibility of remote triggering means you should be leaving a wider margin of error around large, suspect slopes. An avalanche could be triggered from a location well away from the slope. 

Follow disciplined group decision making, ensuring that each group member is engaged in terrain selection. Speak up if you’re uncomfortable or think there’s a better option. Every voice in the group matters.

For more information on managing a persistent slab problem, check out these great articles from Powder Cloud called “How To Manage the Persistent-Slab Avalanche Problem” and “Know Where Not To Go.”

Deep Persistent Slab Management and Mindset

The weak snowpack throughout the BC interior remains a concern and warm temperatures arriving on Wednesday, January 25, are expected to further destabilize any existing weaknesses in the snowpack. Given the volatility of the snowpack recently, we recommend avoiding avalanche terrain, especially in the North Rockies and northern Columbia Mountains. 

While the current weather forecast is showing major warming for the coast and parts of the interior, there is some uncertainty about how warm conditions will actually get and the full extent of this warming away from the coastal areas. The North Rockies appears to be the warmest location in the interior. It is also one of the areas with the most concerning snowpack conditions. 

Freezing levels on Wednesday are forecast to reach over 2700 m for the south coast, 2100 m for the north coast, and near 2000 m for parts of the northern interior. Avalanche Canada Mountain Weather Forecast

The south coast will see the most substantial temperature increases, but the snowpack has already experienced warming and rain earlier in January so the impact of this warming event may not be as substantial as in other regions. That said, we can expect the warming to weaken surface snow and cornices. In parts of the coastal inland region, like the Hurley and the Duffy, a heavy trigger like a cornice falling would be the most likely trigger for any deep weaknesses still lingering in the snowpack.

The north coast has recently seen substantial storm snow accumulation and high danger ratings have been in place for several days. With the incoming warming, we can expect that this storm snow will continue to be reactive to triggering and the danger will continue to be elevated. 

An example of a cornice-triggered slab avalanche. Cornice releases are common during periods of warming and sun, and their heavy weight can trigger deep weaknesses in the snowpack. Photo: Mark Bender

The snowpack structure throughout the interior is weak, and this weakness is expected to persist, potentially for the entire season (see further: The Persisting Problem blog). We’re worried that this warming has the potential to destabilize any lingering instabilities and make the snowpack even more susceptible to human triggered avalanches. 

Recent deep persistent avalanches in the interior include the recent fatal accident near Valemount on Saturday, this nearby deep release near Clemina Creek on Sunday, and a large avalanche near Golden on Monday. In addition to these deep releasing avalanches, we have seen an assortment of other concerning avalanches throughout the interior including touchy wind slabs and persistent slab avalanches failing on a layer of surface hoar from early January. On Monday, these problems resulted in two serious incidents in the interior. 

When the weak layer near the ground is triggered, wide propagations are possible. An example of a deep persistent slab avalanche from early January in the Revelstoke area. MIN Photo from MLDUQ.

We’ve been stressing the importance of conservative decision making and patience in our bulletins and our past blog posts (see further: Managing a Persistent Slab blog) and this is going to remain essential as long as the snowpack is challenging. Our Senior Forecaster, Simon Horton, provides the following advice on managing warming and sun:

Reduce your exposure to avalanche terrain when the temperature is rising rapidly. Be even more cautious it is above zero.

Avoid travelling on or under slopes that are getting hit by the sun during periods of warming. 

The importance of aspect becomes more pronounced during warming. South-facing slopes are more susceptible to the impacts of warming, while north-facing slopes may remain colder.

Be mindful of overhead avalanche terrain.

Small avalanches or cornice falls have the potential to step-down and trigger large avalanches when there is a persistent or deep persistent slab avalanche problem.

Use the power of group decisions. Giving everyone a voice helps groups make better, safer decisions. Speak up if you’re uncomfortable or think there’s a better option.

Watch for increasing temperatures through the day. Even temperatures below freezing have the potential to destabilize the snowpack when weak layers are present. Avalanche Canada photo. 

Given the recent deep persistent slab avalanche activity in the northern interior, we are also advising against riding undisturbed and unfamiliar terrain. Good visibility and mild temperatures should not be seen as an excuse to push deeper into the mountains to find fresh tracks. These are the slopes that are most suspect and have the greatest likelihood of producing large avalanches. Now is a time to stick to simple, low angle terrain as well as busy, tracked-out areas. 

This season’s snowpack is already proving a challenge and the warming will exacerbate that. Keep this forefront in your mind when planning and make the decision to ride terrain that will let you come home safe.

Warming and Weakness in a Complex Snowpack

This year’s snowpack is different from most previous years. Professionals with decades of experience suggest this weak of a snowpack is only seen once every ten to twenty years for much of western Canada. Some professionals are comparing this snowpack to 2003, which was one of the worst years on record for avalanche fatalities. This winter presents a very different set of problems than normal and we need to adjust our mindset to remain safe.

We experienced lengthy periods of drought and cold weather that created numerous problematic layers in the snowpack. The map below shows the status of these weak layers, with the caveat that there are small-scale variations which are better described in the daily avalanche bulletins. The setup of the snowpack varies across the provinces but there is a similar theme for most areas – riders have triggered large, scary avalanches with high consequences.

Avalanches can be triggered from a distance

One commonality we’ve seen is that many of the avalanches were triggered by riders from tens to hundreds of metres away from the slope that avalanched. This indicates that the buried weak layers are widespread and spatially connected, meaning you could trigger the layer anywhere on or near a slope. This is known as remote triggering and is a clear sign of an unstable snowpack. It also means that it is difficult to anticipate where avalanches may be triggered from.

The avalanche was remotely triggered from riders on the ridge above in the Selkirk Mountains (Eric Johnstone photo).

There may not be strong evidence that the weak layers exist

We often suggest looking for signs of snowpack instability to provide evidence that your riding area could be problematic. The complication with this snowpack setup is that the layers are deep enough that we are a lot less likely to see clues, like nearby avalanche activity, whumpfing, or cracking snow. If you do experience any of these then of course it is a strong sign to keep things tame, but right now we must remember that the first sign of trouble could be triggering a high-consequence avalanche.

Riders indicated they did not experience signs of instability before the avalanche in the Purcells (MIN user PURDY.LOGAN)

Many avalanches are triggered where the layers are shallowly buried

We may see a decline in the number of avalanches triggered by riders on these layers as they get deeper. Triggering is less likely when weak layers are buried deeper than about a metre because our stresses are absorbed by the upper snowpack. Where we are most likely to trigger deep layers is where they are shallow, or within that upper metre, which often can be found in wind-affected, rocky terrain.

A wide-propagating avalanche that released on a layer near the base of the snowpack in the Monashees (Vincent Jauvin photo)

Getting caught in an avalanche on this layer could be fatal

Given the widespread nature of these layers and their location deep in the snowpack, a triggered avalanche is likely to be large to very large (size 2 to 3 or more). We’ve seen several near misses of riders triggering large avalanches on these layers and narrowly escaping a fatal outcome. Professionals are treating the snowpack with an abundance of caution given the high consequence of being caught.

A rider escaped being caught in a large avalanche in the Monashees (MIN user MLDUQ)

A weak snowpack will stay around for a while

There’s uncertainty in how long these layers will persist, but it is likely that it could be a season-long problem in some areas. The weak layers have large grain sizes with poor bonding, and it can take months for them to shrink and start bonding as a cohesive snowpack. The season may not be long enough to experience this slow transition, meaning we could see large avalanches from these layers for months to come and even into early summer in the high alpine.

Professionals are stressing the absolute importance of “terrain, terrain, terrain” given the high consequence of triggering these layers. This is the year to be highly conscious about the terrain rather than the snowpack. Discipline and patience will be required to not step out when there is new snow or during a beautiful sunny day. A snowpack like this is unforgiving and cannot be micromanaged. Step back, think of the big picture, and ask yourself if you should be there in the first place.

Here are some further risk management strategies we recommend for areas with a persistent and deep persistent avalanche problem:

Adopt a conservative mindset when in avalanche terrain.

Be diligent about terrain choices, sticking to slope angles less than 30 degrees when in clearings, open trees, and alpine terrain.

Follow disciplined group decision making, ensuring that each group member is engaged in terrain selection.

Minimize exposure to overhead hazard, given that these avalanches can be remotely triggered and travel far in runout zones.

Travel one at a time when exposed to avalanche terrain and regroup in safe spots well away from overhead hazard.

Avoid exposure to terrain traps, such as gullies, cliffs, and trees to reduce the consequence of being caught in an avalanche.

Practice patience, avoid complacency, and accept that you may need to manage this risk for weeks or months to come.

Remember that managing this risk doesn’t mean we can’t have fun. There are a lot of safe terrain features to play in, such as mellow slopes and dense trees. The avalanche forecasts are an essential part of planning for a safe trip. The nuances of the snowpack layers are described in the details tab of the daily avalanche forecasts and offer more information on safer terrain. Until we have clear evidence that this problem may be healing, we highly recommend a disciplined mindset focused on terrain selection.

The snowpack is spooky for much of western Canada

The Persisting Problem

I was just a kid when I first saw the iconic Stanley Kubrick movie, The Shining, but the final shot of Jack Nicholson frozen in the snow after being lost in the hedge maze stayed with me for years. Kubrick nailed it. 

Years later, watching the movie as an adult who spends his days working in remote regions of the Yukon Territory, I can’t help but ask myself, “what could Jack have done to prevent his demise?”. “What are some steps he could have taken to better prepare himself for the environment?”

Every time we make the decision to head into avalanche terrain, it comes with the usual endeavors of planning and preparation. Or, at least it should. The Avalanche Canada Daily Process is something we should all adhere to as we undertake a day of backcountry travel.

However, when it comes to travelling in avalanche terrain when the weather is extremely cold, things get a little more complicated and we need to weight certain steps of our Daily Process more heavily. In particular steps 2 and 3.

So, we’ve checked the avalanche forecast and verified through weather station data that it’s really cold out there. When we go through this process and see these conditions, we should immediately start thinking about consequences. It is a good practice to treat extremely cold temperatures much the same as we would a terrain trap when moving across a slope. The presence of a terrain trap means the consequences of being involved in an avalanche are much greater. The same goes for extremely cold weather. In an avalanche incident resulting in injuries, a race against time ensues. Even with the most ideal winter weather conditions, victims and rescuers often suffer from cold injuries, such as hypothermia and frostbite. In extremely cold conditions, these injuries can occur in minutes—making even minor incidents very difficult and dangerous when the temperature drops.

Extremely cold temperatures should be thought of much the same way as we think of terrain traps– they increase the consequences of being involved in an avalanche. 

Another practice that can also be helpful when adjusting for extreme cold weather days is taking the avalanche danger rating and increasing the danger rating by one level, or adding a +2 to your terrain characteristics when using your Avaluator V2.0 accident prevention card. Either of these approaches help ensure you’re thinking with an appropriately conservative mindset when trying to decide where to ride when the weather is brutally cold. For example, when the avalanche danger is low and it’s very cold outside, we might choose to ride similar terrain to the choices we might make if the danger rating was moderate or even considerable.

Other adjustments we might make when venturing out on very cold days are:

Plan objectives that are less remote and keep us closer to the trailhead or staging area

Plan for shorter objectives and keeping our exposure time low

Stick to simple terrain or non-avalanche terrain (if we are sledding)

Ride in larger groups so that there are more people to help out if someone gets into trouble or suffers a cold injury. (Remember group size has its own risks and rewards though.)

Slow down and build in an extra margin of safety for every decision, even those decisions that seem minor

So we’ve checked the avalanche forecast and weather and have decided to head out even though it’s going to be very cold. We’ve adjusted our mindset to include the potential consequences of the cold and we’re ready to start loading our backpacks and tunnel bags. It’s time to take a closer look at our equipment and the additional items we might include on a cold day. We also need to consider how we might manage certain pieces of equipment differently than we would on warmer days. Some of the things we might consider are:

Ready-HeatTM Vests and Blankets. These are commercially available products that, once opened, heat up due to a chemical reaction. The vest can be worn under a jacket to keep a rescuer or an injured partner warm

Outerwear rated for extreme cold. This includes larger down jackets and down pants, mittens instead of gloves, and face coverings

Extra parts in our repair kits  as things break much more easily in the cold, particularly plastic things

Hockey stick tape to help skins stick when they fail in the cold…because they will. You can also consider putting your skins under your jacket during the descents. This will help them stick better in the cold

Remember items with batteries can be less reliable in the cold. Make sure you bring an extra battery pack and cables to keep electronics charged. If you’re carrying these items close to you to keep them warm, don’t forget they should be 20 cm from your avalanche transceiver in transmit mode and 50 cm when you’re searching. 

Avoid the use of heated jackets and gloves as these  can interfere with the performance of your avalanche transceiver

Finally, consider the implications of having to execute an effective companion rescue and potential patient extraction in extremely cold temperatures. This video from the Yukon Region discusses what those might be. 

Cold weather considerations in avalanche rescue

There are a number of potentially life-saving pieces of equipment we can add to our kit on extremely cold days. An expedition weight down jacket and pants might be at the top of the list.

Ultimately, extremely cold weather adds a layer of complexity to a day in the backcountry. It also increases the level of risk we expose ourselves to. The fact of the matter is, we live in Canada and every winter we experience prolonged periods of very cold weather so understanding the implications of the cold and knowing how to adjust our trip plan and equipment needs accordingly will help ensure a safer outing when the mercury drops way, way down.

Travelling in Avalanche Terrain During Extremely Cold Weather

The stations generally include snow, wind, and air temperature sensors. We use the data to help create forecasts, but they are also valuable for planning your trips into the backcountry.

We recently installed weather stations at Renshaw, Core Lodge, and Telkwa for the 2022-23 season, as well as repairing one in Kakwa. 

These trips often require early morning starts in various weather conditions where, after carefully transporting the equipment to their respective site, we attach each sensor to a tripod and verify their accuracy.

Our stations are found on the map view of www.avalanche.ca and at www.avalanche.ca/weather/stations

Did you know that Avalanche Canada maintains weather stations in data sparse areas?

Avalanche Canada Weather Stations

In the December 10, 2022 public avalanche forecast for Banff, Yoho, and Kootenay National Parks, the primary avalanche problem changed from a persistent slab to a deep persistent slab problem. 

Why did it change and what does this mean?

A persistent slab is a cohesive slab of snow overlying a persistent weak layer (PWL) such as surface hoar, facets, or a crust. The bond between this slab and the weak layer is poor and slow to strengthen, creating a snowpack structure that is prone to failure for long periods of time. Persistent slabs are nasty, but eventually the weak layer strengthens, bonds to the snow above and the problem goes away. This cycle generally lasts four to eight weeks. 

Persistent slabs can form at any time of the winter, usually following a clear period where a weak layer has formed on the surface of the snow and is then buried by subsequent snowfalls. Usually, the problem starts out as a storm or wind slab until forecasters determine it will last an for an extended time, and then they change it to a persistent slab.

Persistent slabs are usually located in specific locations in the terrain. For example, surface hoar is frequently found on north aspects at or below treeline, sun crusts on south and west aspects, and rain crusts on all aspects up to the freezing level. This kind of distribution makes persistent slab problems tricky to navigate and means that managing them requires an understanding of how the layer formed in the terrain.

But what about the classic Rocky Mountain snowpack? The shallow one where the base of the snowpack is rotten and stays that way all year? This is a deep persistent slab. 

A large persistent slab avalanche that failed on a layer of surface hoar in the Monashees in 2010.

Deep persistent slabs begin their life at the start of winter, first as an early-season persistent slab, but the weak layer doesn’t strengthen with time. Instead, changes within the snowpack (metamorphism) make the PWLs near the ground even weaker. These PWL grains are depth hoar, facets next to an early-season rain crust, or even facets sitting on glacier ice. 

Deep persistent slab problems result in a high degree of uncertainty and are characterized by cycles of activity, dormancy, then re-activity; they go to sleep, then they wake up. This on/off pattern can persist for the entire season until the snowpack has melted. So, when that early season persistent slab gets switched to a deep persistent slab, this is a signal that the base of the snowpack is very weak and not expected to improve much.

A large deep persistent slab avalanche from 2012 in the Bourgeau 7 avalanche path above the Sunshine Village road in Banff National Park. Note the avalanche has released on the ground.

Don’t expect this problem to go away any time soon. Hunker down with a conservative mindset and find joy in low angled terrain or the trees. Triggering deep persistent slab problems is common from shallow snowpack areas and wide propagations and remote triggering is typical. Watch your exposure to overhead hazard and recognize that this problem brings a high degree of uncertainty that cannot be reduced except by terrain choice.

Deep persistent slab problems demand a wide margin for error and avoiding specific terrain is sometimes necessary for the entire season. Professional ski guides call this type of mindset “entrenchment” and accepting this limitation is sometimes the biggest challenge of keeping safe when deep persistent slabs are the problem.

Fracture line from a deep persistent slab in ER6 at the Lake Louise Ski Area. The avalanche started on a mid-snowpack layer then stepped down to the ground.

Persistent to Deep Persistent – Why the Switch?

On Friday our forecaster blog talked about a persistent weak layer and the fact that the snow above the weak layer had not yet formed a slab in many areas of the interior. 

Over the weekend, we reached the tipping point throughout many parts of the southern interior and a reactive slab formed, creating dangerous avalanche conditions for many areas. 

Image from near Revelstoke, submitted to the MIN.

Image from the Purcells, submitted to the MIN.

Managing a persistent slab problem can be difficult. If you’re heading out, making conservative terrain choices and leaving a wider margin for error is essential. Here are some strategies AvCan forecaster Josh Smith uses to manage persistent slabs:

I make more conservative terrain choices and leave myself way more margin for error in my decision making. I reduce the likelihood of triggering the layer of concern by avoiding classic trigger spots in the terrain, such as steep slopes, roll-overs, and spots where the snowpack is shallow or thin to thick.

I reduce the consequences of being wrong by sticking to smaller pieces of terrain that aren’t capable of creating large avalanches. I also avoid slopes with terrain traps such as cliffs, crevasses, and deep depressions where even a small avalanche can have deadly consequences. 

I find this easy to do for a few days, but when the problem persists for weeks, I find it takes a lot of discipline to not let my desire to push into bigger terrain get the best of me. However, in my experience, patience pays off when you nail that dream line in perfect conditions.

Remember, some regions may see elevated avalanche danger, while other regions may see lower ratings. However, it’s important to remember that even a moderate danger rating means: “large human-triggered avalanches are possible in isolated areas.” Danger ratings are helpful for getting an overview, but to get the whole picture, you’ve got to dig deeper than the danger rating– this is especially important when dealing with the kind of condition that currently exists.

The only real option at times like this is to scale back and adopt a conservative approach.

Image from near Fernie, submitted to the MIN.

Image from the Selkirks, submitted to the MIN.

Managing a Persistent Slab

Conditions in the interior of BC are tricky right now. Frigid arctic air back in November left us with a widespread persistent weak layer and although avalanche activity on this layer has so far been sporadic, it may increase with new snow, wind, or warming. If you are planning on heading out this weekend, it will be important to be aware of this persistent weak layer and have a conservative mindset. 

The cold Arctic air had two major impacts on the early season snowpack. First, depending on your location, it formed at least one well-developed persistent weak layer which was buried between November 17 and 22 (referred to as the mid-November weak layer). It can easily be observed within the snowpack and has resulted in many observations of whumpfing, shooting cracks, and remotely triggered avalanches, throughout the interior. We have lots of evidence of snowpack test results suggesting that this layer has a propensity for easy triggering and propagation, making it a ‘yellow flag’ to be aware of. However, we aren’t yet seeing the amount of avalanche activity this might suggest. This isn’t because this layer isn’t unstable, but rather because the snow above it has not formed a slab… yet. 

A snow profile from the Mear Lake area north of Fernie shows the mid-November weak layer is reactive and suggests that propagation would be likely if a cohesive slab was present. Photo: South Rockies Field Team

The existence of a highly reactive weak layer on its own is not enough to create a persistent slab problem that elevates avalanche danger. A persistent slab problem requires both a persistent weak layer and a cohesive slab on top of it. This brings me to the second condition caused by the extended periods of cold arctic air and a generally shallow early-season snowpack—an apparent lack of slab formation in many parts of the interior. Because of the prolonged cold conditions, the recent storm snow has not settled in many areas and may even be doing the opposite. The entire relatively shallow snowpack may be undergoing faceting in some regions. This is keeping the snowpack unconsolidated and prevents the formation of a cohesive slab.

We know there is a widespread weak layer throughout the interior, and therefore we would expect avalanches to be possible anywhere that a slab has formed. But the ongoing cold conditions mean it is difficult to know where slabs may exist.

An example of the type of smaller avalanches we have been seeing a lot recently. As the slab becomes more cohesive, we expect the size of these slabs to become larger and propagate more widely. Photo: Skiing Golden, submitted to the MIN

An example of remote triggering, with the slope being triggered from the adjacent flat terrain. At this location/elevation, the slab may not be thick enough or cohesive enough to form a destructive slab, but this is a strong sign that the layer may be capable of producing large avalanches where the slab is thicker or more cohesive, such as at higher elevations or in more wind loaded terrain. Photo: Blaseror, submitted to the MIN

We commonly refer to the period where loose surface snow transitions into a reactive slab as ‘the tipping point’. There are several conditions that may cause the current loose surface snow to transition to a reactive slab including:

A major storm system bringing a substantial amount of new load over the weak layer.

A warming event or extended periods of solar radiation on steep sun-exposed slopes. 

A combination of slow snow accumulation with an extended period of milder temperatures. 

We have seen a few of these conditions, especially wind loading, result in some large avalanches over the past couple of weeks. Wind loading has also been one of the main messages in our bulletins recently. Although we’re not expecting substantial warming, just a few hours of sun on steep sun-exposed slopes can be a major player in the likelihood of triggering an avalanche, as the example below shows. 

A period of sun caused enough warming for the upper snowpack to settle into a slab resulting in this avalanche on a SW aspect which failed on the mid-November layer. This is a good example of the type of avalanche we would expect where a slab can be found above the weak layer from mid-November.  Photo: Mikey, submitted to the MIN

For now and in the immediate future, we likely can expect danger to remain elevated as slabs form over the buried weak layer. It will be important to watch carefully for any signs that the upper snowpack is settling into a slab and ensure your plans match the conditions. 

For more details on persistent slab problems, check out the video about Persistent Slabs on Avy Savvy. 

The Waiting Game

Daily avalanche forecasts have started for most regions! Over the past few weeks, avalanches have only been an isolated concern at upper elevations where there has been enough snow to cover rocks and trees. Now a steady stream of winter storms is forming a deeper layered snowpack in alpine and treeline terrain and helping the snowpack reach the threshold for avalanches below treeline.

Stormy weather over the weekend looks to bring another 30 to 50 cm of new snow to most of the mountainous regions of western Canada. Expect danger ratings to rise in response to increasing amounts of new snow. Forecast region boundaries will also shift with the incoming storms, reflecting changes in conditions. The main factor determining our region boundaries this weekend will be forecast snowfall amounts. For example, you may see large regions covering areas where snowfall amounts and avalanche danger will be relatively uniform.

With the transition to winter conditions, it is important to remember that avalanche danger can increase dramatically as you climb into higher terrain and as you transition from shallow snowpacks below treeline, to deeper and potentially more dangerous snowpacks at treeline and in the alpine. Remember to gear up with a transceiver, shovel, and probe and factor these dynamic avalanche conditions into your plans!

AvCan team hard at work preparing for the first forecasts.

Winter conditions and daily forecasts!

Why is everything grouped into one large region?

With our new forecasting system, our forecast regions are dynamic, with boundaries that change in response to conditions. Areas experiencing similar conditions are grouped together. This means the avalanche.ca map will look different this season. Currently early season conditions prevail across Western Canada, which means we’re displaying one large region with one forecast. If you're out in the mountains, approach steep snow-covered slopes with caution and be sure to take a transceiver, probe, and shovel. Remember, "If it's deep enough to ride, it's deep enough to slide."

As we get more information about conditions in various areas, our forecasters will start to create more regions. We’re expecting this to start happening early next week.

Even though the map will start to change, we won’t be issuing forecasts until November 25. You still won’t see the usual avalanche danger ratings or problems, but we will add notes into the ‘details’ tab of the forecast to help you plan your trips in the meantime. 

Find out more about flexible forecast regions here.

Get more information on early season conditions here.

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