Before we begin, the obvious must be stated:

The mountains are dangerous places and no matter your training or experience, stepping out into big, complex terrain comes with increased risk no matter how perfect the conditions may be. 

Most of the big lines go down in the spring after the snowpack has transitioned from a complicated stack of weak layers to more uniform layering; and a daily cycle of warming up during the day and freezing solid at night. The golden rule for attempting big lines under these conditions is to START EARLY (ie. Zero-dark-thirty)!

The reason for this is simple: the avalanche danger starts at low when things are frozen and then rapidly increases during the heat of the day. The pros will get to the top of their line just as the top few centimetres of snow is beginning to soften and will be sure to be out of avalanche terrain before the slushy snow gets ankle deep.

Starting in the dark is standard practice when tackling big objectives. Photo: Drew Nylen

Get to know your local snowpack. A big line that may be reasonable to attempt on the coast could be a suicide mission if it was in the Rockies. I’m not suggesting never attempting big lines in the Rockies, but understanding the local snowpack is key. 

Here is a list of conditions that I look for before I consider big objectives in complex terrain:

Avalanche danger rated as low with no persistent slab problem.

No recent avalanches reported in the area I plan to visit.

Stable weather, with no recent or forecast weather that would increase danger such as: 
- Warming, including rising freezing levels with temperatures nearing 0 C in the alpine or strong sunshine. Yes, sunny days are great for big objectives, but not if forecast is for full sun AND temperatures nearing 0 C.
- Ridgetop winds greater than 25 kph.
- More than 10 cm of recent snow

I keep my group small. Four or fewer partners that have the appropriate training, experience, and personal risk tolerance for the objective is an ideal group size.

"No-fall zones"-a slip in steep alpine terrain can have serous consequences. Photo: Alex Cooper

Avalanches aren't the only hazard when skiing big lines. These are some others:

Falling hazard: Generally when avalanche hazard is low, falling hazard is high. A fall in steep terrain or over a cliff can have fatal consequences. Does everyone in the group have the skills to get up and down the line without falling? Are they comfortable traveling in “no-fall” terrain?

Cornices: Many avalanche professionals can tell stories of personal close calls with cornices failing under their feet while traveling on ridgetops. Be very wary of cornices and give them a wide berth.

Crevasses: Often, glacier travel is required to access big lines. Do you and your partners have the appropriate training and experience?

The top riders sometimes wait years for conditions to be just right on the big lines.

A few years back, I was attempting to ski off the summit of Denali (N. America's highest peak) via the Messner Couloir. When my partner and I arrived at the 14,000 ft. (4,267 m) camp and we got our first glimpse of the line, it looked more like an alpine ice climb than a ski line. However, snow was in the forecast and we waited patiently for a week in -30 C temperatures in hopes of enough snow sticking to the blue ice to make the line skiable. 

Finally, when we felt the conditions were just right, we left camp in the wee hours of the morning, punched it to the summit, and skied the 1,500 m, 45-degree couloir in boot-top pow that had stuck to the ice.

We returned to our camp overjoyed with a deep sense of accomplishment. The months of planning and three weeks of enduring frigid temperatures was all worth it.

In the words of Yoda: “Patience, you must have.”

Warming up on the 'rescue gully' prior to skiing off the summit of Denali. Photo: Joel Bettner

Josh Smith is an ACMG ski guide and public avalanche forecaster

If you stare up at the big peaks and dream of nailing those big, steep lines in complex terrain, this post is for you.

Going Big: How to Approach Big Lines

Whether it’s the sound of birdsong returning to your local woods, the sight of bustling local patios, or the whirring of bike hubs steadily rising on streets and trails like a B-movie insect invasion, you’ve likely begun to observe signs of the changing seasons. The great helmet swap is upon us once again!

If you have been holed up in an alpine hut for the last month or so, you could be forgiven for not noticing the change. This is because in many areas of the province, to borrow a phrase used by Glacier National Park forecasters, “There are two snowpacks in the region at the moment.” 

Below about 2,000 m in elevation, true spring has arrived. Regular melt-freeze cycles have formed thick surface crusts and lower elevation snowpacks are melting away. Above 2,000 m, winter has been slow to loosen its grip. Sure, solar aspects have formed an impressive tally of crusts as a result of ever-increasing solar warming on days the sun is out. But on north aspects, we still have cold, dry powder stashed at high elevations, away from the influence of recent, moderately high freezing levels and intense sunshine.

There’s more to spring than just wet loose avalanches. An April 27 image from MIN user PackedPow highlights a human-triggerable wind slab in the alpine of the Sea to Sky region. 

Perhaps most importantly, the snowpack at alpine elevations has yet to experience the kind of sustained warming event we normally would have felt by this time of year. This warming, when it occurs, will bring a final test to our season’s deadliest weak layer—a crust and facet combo formed in early December that is lurking near the bottom of the snowpack. Only after this test will we become confident we’ve transitioned to true spring conditions. While we wait, our uncertainty lingers. Will we get big spring avalanches running on deeply buried weak layers? The answer isn’t yet clear.

Debris from a size 4 avalanche in the runout of the Greenslide avalanche path south of Revelstoke in May 2017. Could we see a repeat in 2022?

Spring is a complicated time. The significant variation in conditions presents challenges to die-hard winter aficionados. To capture their variability, Avalanche Canada and our partner organizations outlined four scenarios for spring conditions messaging. Three of these scenarios have already been in play in most regions: All Freeze No Melt, Cold and Snowy, and Daily Melt Freeze Cycles. If you see one of these scenarios suggested in your region, the associated advice will serve you well. 

The missing player here is All Melt No Freeze. Fortunately, the description and advice attached to this scenario applies really well to what we’ll want to convey when it does eventually emerge. The tough part for us as forecasters is accepting we won’t be around to slap a danger rating on the forecast, write an attention-grabbing headline, and jump on social media to shout the message from the mountaintops. We’ll be monitoring the situation into early May, but as it stands right now, the weather doesn’t look to be delivering a real big warm-up before then. Since you must act as your own forecaster in our absence, we want to emphasize a few points to help you manage the coming period of uncertainty.

A little sun does a lot. We’re currently getting the same amount of solar radiation we see in late August. When the sun comes out, expect warming to be intense and for surface snowpack layers on sunny slopes to lose cohesion and stability quickly. 

How thick is the crust? This is one to monitor over the course of each day. Once enough surface melt has occurred that the crust fails to support your weight, conditions are getting dangerous. Wet loose avalanches become more and more likely and the possibility for deeper weak layers to reach their tipping points gets more and more real. You do not want to be in the vicinity of a large wet slab running on a deep persistent weak layer!

Cornice fall analysis. There aren’t as many professionals out there digging profiles and testing the snowpack as there were a few weeks ago. Fortunately, cornice falls are a very effective, all-natural test of snowpack stability. Think of them as a probe deep into the snowpack. There are lots of cornices still hanging out over north-facing slopes. If you see one break off and trigger a slab, this is a really important piece of information. If they tumble down a slope uneventfully, there’s a good chance you won’t trigger an avalanche on a similar slope either.

Keep an eye on the MIN. This is one part of avalanche.ca that will remain live through the end of the season. Sharing is caring! Report your observations and check out those of others in the community to keep your finger on the pulse.

Watch for a big warm-up. This means staying tuned to weather resources like Avalanche Canada's Mountain Weather Forecast and SpotWx. Look out for a multi-day period of freezing levels that are above mountaintop elevations in your region. Clear overnight periods may allow for reasonable crust recovery during a time like this, but if overnight cloud cover or high elevation rain are also involved, we’re definitely in the zone where the alpine snowpack will undergo some serious testing.

With a winter snowpack still in place in the alpine, dramatic changes to the snowpack are both possible right now and certain to occur in the future. Avoid being lulled into a sense that spring’s arrival means avalanche season is over. We aren’t there yet!

- Colin Garritty and the forecasters at Avalanche Canada

Avalanche forecasts are done, but you should remain wary of a major warm-up as spring progresses.

That's a Wrap! The Forecasting Season Draws to a Close

This week’s warm weather has the potential to produce large avalanches across southern BC and Alberta.

A week ago, we saw a single day of warm, sunny weather produce large and very large avalanches across many of the coastal and interior regions. The photos below illustrate some of these avalanches. This week’s weather has the potential to produce similar results.

Forecasting for this kind of activity can be tricky, as sometimes warming produces only small wet loose avalanches. But given the time of year and the complex layering in the snowpack, we are concerned about the potential for this warm up to produce large, surprising avalanches that are more than capable of burying a person. They may be storm slabs in the recent snow, persistent slabs on older layers, wet slab or wet loose, or even just large cornice falls.

Because of these uncertainties, it’s best to choose more conservative terrain during this period of intense warming and sun exposure. Conditions will become more predictable in a few weeks once the snowpack has completed its transition into spring. For now, this type of warming should be treated with extra caution.

A deep persistent slab avalanche in the North Columbia region, reported on March 29.

Natural avalanches in Loop Brook, Glacier National Park, observed in a MIN report on March 31.

Slab avalanche observed by the Avalanche Canada South Rockies field team in the Lizard-Flathead region on March 30.

Natural avalanche observed in the Sea to Sky region, from a MIN report on March 31.

Photos of avalanches from last week’s warming could be a sign of things to come

Early April Warming May Produce Large Avalanches

(and why we’d love to see your post, whoever you are!)

The Mountain Information Network (MIN) is one of our most powerful tools for creating accurate forecasts and planning backcountry trips. And the best thing about the MIN is that it gets better when you use it—the more people post, the more useful it becomes. So, we’ve been on the lookout for the reasons people use for not posting. After much deliberation (ok, maybe only a little deliberation) we present the top five reasons you might not be posting to the MIN, and our reasons why we’d love you to post anyway:

"I don’t know enough"
Even if it’s your very first time in the backcountry, you’re qualified to write a MIN! All you need to do is share what you see. Some of the most helpful MINs we see don’t contain any technical language at all, but they do give a good description of what people noticed. Here are some things you might be able to share in your report:
- What weather you saw
- What the snow felt like under you or your machine
- Any cracking, whumpfing, or signs of avalanches you noticed
- How the riding was


"Nothing happened"
Sometimes, knowing what didn’t happen is every bit as important as knowing what did. Letting us know conditions were as expected helps us with accurate forecasting. Validating our forecasts is important and very tricky for us to do. Letting us know what you saw was in line with the forecast helps us build a more accurate picture of what is happening. And the better that picture, the better your forecast.


"I don't want to blow up my spot"
We get it. We wouldn’t ask for you to share your secret spots. Tagging a location close to the good stuff is enough to be useful. Choose the staging area, a nearby road or landmark, or an area close-by that is already busy. Any of those options allow us and other recreationists to see what conditions were like, while keeping your secret stashes secret. Read our blog on how to give the info without giving up the goods.


"I don't want people to judge me"
It’s hard to post something publicly if you think there will be backlash. The good thing about the MIN is there’s no option for people to offer feedback on your post. It’s simply a forum to share  information. There’s no judgement here. In fact, we strongly value talking about mistakes we might have made in the backcountry. We’ve all made them and if we can learn from others, all the better. Whether it’s about a mistake or a weather report, every post is a piece of information that could keep someone else safe. We appreciate them all!


"Conditions are good. Why would I share that?
We like to think there’s enough backcountry for everyone to enjoy. You don’t need to sign post the way to the best snow in your report. Keep the location vague, but remember good conditions are still conditions, and the more we know, the more accurately we can forecast. Posting that you had an epic day on the MIN helps us to understand more about how the snow is behaving and what might happen next.

Want to learn more? Here are some extra resources to get you started on your MIN journey.

Information on how to use the MIN, including some helpful tips on acronyms you might see used

Watch our webinar about using the MIN and how to make the most of the posts you read

Having technical issues with our app or website? Let us know by emailing support@avalanche.ca

A spotty but consequential problem

Whumpfs and remotely triggered avalanches have returned to the Sea to Sky forecast region, and areas in the South Coast Inland like the Duffey Road and Coquihalla. These recent avalanches mean there’s potential to trigger slides accidentally from a distance, including “toe triggering” or releasing the slope above you from a spot you wouldn’t normally consider steep or risky.

Thanks to Evan Stevens (zenithguides.ca) for this photo from the Blackcomb backcountry on Wednesday.

This photo taken in the Brandywine area Thursday.

We use past avalanches to forecast future ones. And several similar avalanches suggest we have a trend, not just a weird one-of-a-kind to gawk at and forget. Here’s a sketch of the snowpack structure to help picture the problem.

Here are some more examples of MIN reports from the past week highlighting whumpfing and avalanche activity suspected to be running on the same buried weak layer. Here, here and here.

This kind of layering doesn’t just heal and disappear in hours or days. It’s likely to remain for days to weeks. Plan on it being problematic at least through the weekend as Evan Stevens pointed out in his recent South Coast Touring Group post. Similar conditions about one month ago caught several people off guard.

There is some uncertainty for how this layer will react in the coming days. A higher level of uncertainty should affect how we manage the problem. If you’re looking for a little neighbourly advice, here are some ideas:

Pull in the reins. Adopt a conservative approach to choosing terrain. Be disciplined about maintaining that approach.

Avoid steep, convex, unsupported slopes at treeline and in the lower alpine.

Stay away from thin/variable depth/rocky avalanche terrain.

When the sun comes out after a cool period, loose snow sluffs out of steep terrain and cornices can begin to fall. Small avalanches and cornice falls add significant weight to the slopes below and increase the chance of triggering buried weak layers. Take stock of what is above you and minimize your exposure when the sun is out.

Tricky snowpack structure returns to the coast

The early December crust/facet persistent weak layer (PWL) is now a well-established feature of this season’s snowpack. The atmospheric river events that created this layer were unprecedented, in terms of their intensity. But the resulting layer is not. We’ve seen these “rain on snow” events before, and those experiences provide us insight into how things might play out in the coming weeks and months.

The winter of 1996 – 97 had many similarities to this season. In early November, a rain on snow event occurred from the Coast Ranges all the way east to the Rocky Mountains. On Nov 11, that wet layer was buried by dry snow. Then an Arctic air mass took hold and froze the moist Nov 11 layer, resulting in a widespread crust under the dry snow.

This combination of moisture and cold temperatures produced a layer of facets on the crust, which resulted in a PWL that produced large, destructive avalanches throughout the winter and into the spring. The 96 – 97 mid-November crust/facet PWL proved to be deadly and was linked to seven of the 13 avalanche fatalities that occurred that year. 

Avalanche Canada avalanche technician Ben Hawkins holds up a 3 cm thick crust found with overlying facets in his snowpit (file photo).

If you want to dive into the science of rain on snow events and crust/facet PWLs read this article by Dr. Bruce Jamieson: The Facet Layer of 1996 in Western Canada. Crust/facet layers are very diverse in how they form, how they bond to layers above and below, and how they evolve over the season. Generally, strength and bonding fluctuate, giving us periods where they are reactive interspersed with dormant periods when they are largely unreactive. While it’s hard to say definitively how this season’s crust/fact PWL will play out, the AvCan forecasting team is increasingly thinking this layer will remain a problem in the Monashees, Selkirks, Purcells, and parts of the Rockies for the remainder of the season. 

This layer is known to exist in parts of the South Coast ranges and it’s possible that it will come out of dormancy there later in the season. And it’s possible we’ll see it come to life in other places where it’s not yet been a significant problem.

We’re now in what’s called a low-probability/high-consequence scenario, which means avalanches on this layer are not easy to trigger, but those that do occur are often massive, even historical. Like the one that occurred on January 22 in the Jack Macdonald avalanche path east of Revelstoke near the western boundary of Glacier National Park. 

Debris from a size 4.5 avalanche covers the avalanche shed at the Jack Macdonald avalanche path in Glacier National Park. 

Natural triggering in this situation often involves things like cornice falls or step-down avalanches, where a slide initiates higher in the snowpack, then overloads and triggers the deeper PWL. Human triggering most often occurs in shallow snowpack areas or where the snowpack depth varies significantly across a slope. For both human and natural triggers, the likelihood of avalanches involving a PWL is higher when the weather changes.

The early December PWL is here to stay in many parts of western Canada. There may be periods of time without large avalanches but that doesn’t mean it’s gone. Here are some things you can do to reduce risk for the rest of the season where this layer is a concern:

Stay away from variable depth snowpacks where thick to thin areas exist.

Reduce exposure to tracks and runouts of large avalanche paths, right down to valley bottom.

Eliminate exposure to avalanche terrain at the onset and during weather changes, and keep it dialed back for a few days after. Weather factors that sensitize PWLs include:
- New snow or wind loading, especially rapid loading.
- Rain.
- Temperature changes, especially rapid changes from cold to warm.
- Strong solar radiation, especially a sudden onset such as early morning on sun-facing alpine start zones, or when clouds open and the sun pops out during the day. 

Every season is different. Last season was filled with epic stories of first descents in aggressive terrain, but these kinds of activities carry more risk this year. This year is all about the long game. It takes patience and discipline to keep these long-term problems in mind every day, and ongoing vigilance to recognize when and where the layer is likely to be more sensitive to triggering. 

Avalanche Canada forecaster, Zoe Ryan, conducts a recent propagation test in the Corbins area near Glacier National Park. See the full video with sound. 

By Tyson Rettie,  Avalanche Forecaster, and Karl Klassen, Warning Service Manager

The Crust That Never Dies

This weekend, Avalanche Canada, in partnership with Parks Canada, issued a Special Public Avalanche Warning (SPAW) for several regions in the southern half of BC and western Alberta. Our concern is the warm temperatures and clear skies in the forecast, which will destabilize buried weak layers in the snowpack.

We have written previous articles detailing activity associated with these layers, including this blog from Dec 30 and this photo essay from Jan 5. The large, spooky, mostly human-triggered persistent slab avalanches on the December layer really makes the hairs on the back of my neck stand up!

I’ll add a couple of more recent images to hammer home the point: the December weak layer cannot be trusted. 

This skier triggered event occurred at North Tombstone in the Lizard Flathead region and was submitted to the Mountain Information Network on Jan 15. Credit: MIN user FBS.

This size 4 avalanche occurred in the Sea to Sky region on January 15. This gives a harrowing perspective of the scale that we’re talking about here. There are additional photos of this event at the bottom of this article. Photo credit: Powder Mountain Snowmobile Club.

Previous patterns of avalanche activity have told us that the December layer is most likely to become active during periods of warming. Guess what? There is a big, warm ridge poised to affect western Canada starting today (Friday Jan 21), extending through the weekend and into the start of next week.

There are some nuances to how the warm weather is likely to come in, depending on where you are. Looking at the map below, we can divide the area of concern into two broad zones: a coastal zone that also includes much of the Kootenay Boundary region, and an interior/Rockies zone.

In the coastal/Kootenay Boundary zone, we’re expecting broad-scale warming that will affect all elevations. You can see this illustrated in a different way using a freezing level timeline below.

This freezing level timeline is for Brohm Ridge north of Squamish in the Sea to Sky region. The bold red line indicates the freezing level and the zone of warm air is annotated on the chart. By around noon on Saturday, warm air is expected at all elevations.

Contrast the pattern above with a freezing level timeline from the interior/Rockies zone.

This freezing level timeline is for Fidelity Mountain in Glacier National Park. The upper, oval-shaped line marked with an “0” indicates an inversion, with above-freezing temperatures at higher elevations. In the interior/Rockies zone, we’re more likely to see cooler mid-elevation temperatures, but alpine areas will be warm with plenty of sunshine.

The likelihood of an avalanche will be linked to three main factors this weekend: how warm it is; how sunny it is; and the structure of the snowpack.

Areas that harbour weak layers and get hit with a double whammy of warm temperatures and sun are the most likely to produce very large avalanches. However, where the snowpack structure is inherently weak, experiencing only one of these weather factors (either warming or sunshine) may be sufficient to trigger a large avalanche.

Many professionals have described the current snowpack as “untrustworthy”. Combine that with a very significant warm-up and it suggests this weekend is not the time to seek out big lines. If very large avalanches do occur, keep in mind they can run beyond historic path boundaries and trim lines. So it is essential to understand where you are in the terrain and what is above you at all times. 

Best advice is to stick to simple and/or small terrain that is insufficient to result in a burial if the slope was to slide. Find a low angled slope and soak up some rays!

Additional photos of the Jan 17 size 4 avalanche in the Sea to Sky region. Photo credits: Powder Mountain Snowmobile Club.

Avalanche Canada has issued a Special Public Avalanche Warning. Read on for an explanation of what forecasters are thinking.

Untrustworthy snow - explaining the SPAW

Since posting the original article on this subject, several questions have come up. In this follow-up I’ll do my best to respond but remember I’m a guide and avalanche forecaster, not an electrical engineer. I can’t offer definitive answers on the more technical questions, but I can give you my perspective as an avalanche practitioner and pass on what I’ve learned by talking to experts in the field. 

Question 1: Does airplane mode make any difference?

On my phone, airplane mode turns off some but not all transmit/receive functions. When airplane mode is on, Wi-Fi and cell signals are turned off but:

·        Bluetooth remains active; and

·        I’m still getting positional and tracking functionality in mapping apps, so GPS remains enabled. 

Given this, it’s my opinion that the only way to eliminate potential active interference from your phone is to turn it off. 

We know turning off isn’t realistic or practical in all circumstances. So, if you decide not to power down completely, then turn off functions you don’t need (e.g., Bluetooth) and using airplane mode are at least a partial solution and it’s probably better than nothing. 

Question 2: What about heated clothing, heated googles, googles with fans?

Anything that uses electricity is a potential source of interference. When these items are turned on, you’re dealing with active interference. And even when turned off, the battery, metal components, and wires in the equipment are potential sources of passive interference. The more wiring and the more current being used, the more I worry about interference. And anything that surrounds or covers the transceiver is a no-go.

So, heated jackets—nope; not ever in any circumstances. Heated gloves must be turned off and stowed in your pack when searching. Same for goggles. Heated socks should be turned off and be careful to keep your distance when you’re in fine search mode, with your transceiver close to the ground and near your feet.

Question 3: Many snowmobiles have Bluetooth. Will that make a difference?

Even without Bluetooth, sleds are a source of active interference when they are running. Electricity is flowing and that creates an electromagnetic field. 

And yes, a sled with Bluetooth adds another dimension to the problem. I’m not sure how Bluetooth works in these sleds. If the Bluetooth still functions when the engine is off, then you need to figure out how to turn it off or you need to keep it 25m away from the search area. 

Electronic devices on newer sleds may cause interference. 

If, like other electrical activity, Bluetooth gets shut down when you turn the machine off, then you are just dealing with a rather big chunk of metal which is, of course, a potential source of passive interference. 

Question 4: Are some brands of transceiver better than others in terms of interference? 

I’m not aware of any research or test results that indicate a difference in transceiver brands regarding this issue. Given that all transceivers use the same frequency and the same fundamental principles to send and search for signals, I suspect there’s little or no difference between brands. 

If you’re concerned, I suggest contacting the manufacturer to see if there are brand-specific features or functions for managing/mitigating interference, then choosing a transceiver that you’re most comfortable with.

 Question 5: What about medical devices?

Any medical device that has metal or foil components must be considered a potential source of passive interference. Any medical device that has a battery, uses electricity, and/or sends/receives signals is a potential source of active interference. 

Now, with medical devices we’re solidly in the realm of balancing risks. Obviously, you don’t want to turn off or disable a device that’s keeping you healthy and alive. So, you’ll need to figure out how to mitigate interference while using these devices.

I strongly suggest you check owner’s manuals or contact the manufacturer of your medical device and transceiver for advice. Barring contrary advice from the manufacturer, at least keep your transceiver a minimum of 20cm away from your medical device when in send mode and 50cm away in search mode. And learn the strip search technique in case you do end up in a situation where you can’t fully mitigate interference.

If you are getting signs of interference near power lines, I can’t think of any way to mitigate this other than learning the strip search technique. Same goes for buildings and electrical machinery, motors, etc. 

 Question 7: Do smartwatches interfere with transceivers?

I can’t think of any situation where a smartwatch is an essential piece of equipment, although I admit I’ve never used one so perhaps I’m wrong. My advice is turn off your smartwatch and stow it in your pack, if not at all times, then for sure when searching.

I completely forgot to discuss packs and airbags in my original article. So, here’s my take.

All packs are potential sources of interference—there could be metal components (e.g., buckles or stays) and almost certainly there are metal contents (shovel, probe, etc.). No matter whether it’s an airbag or not, your pack is an essential piece of gear. In most companion rescue situations, dumping your pack isn’t a realistic option. 

Airbags driven by a compressed gas canister can be treated as a source of passive interference. Figure out where the metal components are (remember there are probably metal parts or wires involved in the trigger mechanism) and wear your transceiver in a way that maintains at least 20cm separation from those components. Battery-powered, fan-driven airbags require the same 20cm separation when in send mode. 

Things change when in search mode. If you’re using a compressed gas airbag, it is a source of passive interference, and you need to keep your transceiver at least 50 cm away. You can usually achieve this by holding your transceiver in front of you and on the opposite hand from an airbag trigger.

A battery-powered, fan-driven bag is a different story. Like any other electrical device, it’s a potential source of active interference. You must decide whether it’s safe to turn the airbag off while searching. If yes, then do so and use the same 50cm separation as described above for passive interference. But if you’re in a situation where you don’t feel you can turn it off, you’ll need to mitigate as best you can. Change where you hold the transceiver while searching, shift the pack a bit to increase the distance from the transceiver as much as possible, and, if all else fails, use strip search techniques. 

 Airbags and radios can both be sources of interference. 

Question 9: How do I test for interference?

This is a highly complex problem that defies a simple ‘one size fits all’ approach to testing, given the huge array of potential connections and interactions between devices and signals. The experts I consulted were very reluctant to consider testing as a solution to this problem, saying that there’s no surefire way to provide definitive answers. 

With no comprehensive guidance on how to test effectively, my real-world strategy revolves around preparation, awareness, and backup search strategies. Here is my approach:

1.      Turn non-essential devices off and stow them in my pack. Maintain adequate distances between transceiver and interference sources.

2.      Stay vigilant. If I see strange or unexpected behaviour when working with a transceiver, recognize problems early and assume it’s interference.

3.      Mitigate the source(s) of interference.

4.      Use strip search techniques if adequate mitigation isn’t possible. 

If you go to the International Snow Science Workshop archive and put the word interference in the search field, you’ll find links to some historical papers on the topic. A Google search on “avalanche transceiver interference” will turn up some additional information. And the coming issue of The Avalanche Journal has an article on interference that contains some test results.

 Question 10: I’m wondering if a Faraday pouch or lining my phone pocket with Faraday tape would block the interference caused by the phone signal?

Faraday tape and fabric is intended to block electromagnetic radiation. In theory, keeping your devices in a Faraday bag or pocket would stop potential active interference. But this would also block incoming calls and communications with other devices. Similarly, a navigation device would not be able to receive GPS signals so tracking functions won’t work while the device is in a Faraday enclosure.

So, while there are probably some potential benefits for specific scenarios, you’re going to have to live with limitations. If you do decide to go this way, remember that the Faraday enclosure is an additional source of passive interference and will almost certainly be highly effective in blocking transceiver signals if you’re not careful. Just like you keep it away from other metal or foil objects, be sure to keep your transceiver away from a Faraday pouch or pocket.

 Forecasting supervisor, James Floyer, checks his phone before turning it off and stowing it away from his transceiver. 

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