Forecaster's blog

NOT Just General Spring Messaging - Touchy Persistent Slab Problems in the Interior and South Coast Inland

Shannon Werner, Joe Lammers — Mon, 22 April 2013 16:00:00

Spring is just around the corner yet again. However, winter is still holding on and is in full effect especially above treeline and into the alpine. If you're headed out into the mountains with some big spring objectives, ski traverses or hitting the throttle before the sled gets put to bed, please read below. We have some highlighted concerns in the Purcells, Columbias and parts of the South Coast Inland that go beyond your typical spring messaging.

In the beginning

If you remember back in late March, spring-like riding and avalanche conditions prevailed province wide. The valley bottoms became snow free and summer sports gear made its way out of storage units. Sunny skies, high freezing levels, and diurnal temperature swings were the theme, which made avalanche conditions somewhat easier to predict as long as you had a good understanding of aspect, elevation, temperatures and initial signs of instability. With spring-like conditions you can generally travel fast, far and hit those bigger lines and objectives that you've been starring at all winter long.

What happened to the snowpack during that time?

Generally, the snowpack became well settled and consolidated. Surface snow became moist during the day then re-froze overnight forming a melt-freeze crust, while upper northerly aspects were able to hold onto some dryer, wintery snow.

Then the inevitable happened: surface hoar growth. Darn! Yet it was no surprise with the cooler, clear nights. Surface hoar formed on all aspects just before it started to get buried by incremental amounts of snowfall within the first week of April. We called this the "Easter Surface Hoar" and by April 5^th a more substantial frontal system unloaded moderate to heavy amounts of precipitation over the regions burying the problem.

What's happening now and what's the problem?

The Easter Surface Hoar layer is lingering...

Many regions have received 15-30 cm of new snow over the past few days accompanied by moderate W-NW winds. Upper elevations have remained colder and recently clear through the period. Slab properties overlying the weak interface have changed overtime becoming stiffer, more cohesive and recent solar effects may also influence some of these changes.

The regions that are highlighted below have ongoing elevated avalanche concerns:

Purcells

On Sunday April 21^nd (the last day of issued Avalanche Bulletins) an incident report was submitted from the Caribou Creek area near Golden. Five sledders were riding along the ridgeline and remotely (from 100 m away) triggered a size 2.5 and a size 3 slab avalanche from NE-SE aspects. Additionally, a natural cornice fall size 3 initiated a slab on the slope below, which in turn stepped-down deeper. All avalanches had significant wide propagations with the culprit failure reportedly being the Easter surface hoar or surface hoar/crust interface.

North/South Columbia

A number of large avalanches were reported on this layer last week, including a size 3 on the NE face of Cougar Mountain over the weekend. Again, it appears as though the places you're most likely to find touchy avalanche conditions are on high elevation slopes exposed to wind and/or solar influences. What's Next for the Interior?

The negative:

Persistent slab problems are hard to predict and they are usually a low probability, yet high consequence scenario resulting in large-very large slab avalanches.
They linger, waiting for a trigger.

The positive:

Overtime, the weak interface will eventually start to form a bond to the slab above.
Forecast rising freezing levels, and sunny skies will likely promote more upper snowpack instabilities and an increase in avalanche activity. Cornice fall and smaller avalanches may be enough to trigger the lingering weak interface below creating large avalanches and possibly help clean out the problem.

Travel Advice and Suspect Slopes for the Interior

Earlier this week the pattern began with very large avalanches from neighboring regions. These avalanches were remote heli, machine and skier triggered. Slopes to be weary of and ways to help mitigate risk are listed below:

Suspicious slopes are large, steep upper elevation North-East through South-East aspects.
Use smaller test slopes that resemble your larger objective. Dig down and test the weak interface before dropping into larger slopes of higher consequence.
Conditions can change quickly with elevation. Monitor this and make observations as you travel.
Keep an eye on the weather, rapid weather changes will directly affect the snowpack. In response, avalanche hazard can change rapidly.

South Coast

Some areas within in the South Coast Inland region are also plagued by persistent weaknesses which are somewhat uncharacteristic of the region, as well as the time of year.

During early April's warm, dry spell most surfaces were under a daily melt-freeze cycle. These surfaces were eventually buried as crusts. During the dry spell, however, the highest north-facing slopes stayed cold and weak surface hoar crystals were able to develop. Since then 60-90cm of snow has fallen and these accumulations have settled into a cohesive and variably reactive slab. The data sparse nature of the region has made it tough for us to lock down exactly where this weak structure exists, or doesn't exist; however, hot spots seem to include the Duffey, Birkenhead, Railroad Pass and Goldbridge areas. We know this because a number of highly experienced big mountain riders have been surprised in these locations triggering avalanches destructive enough to kill. See our Incident Report Database for details.

The weak surface hoar was buried on April 5^th, but 2 weeks later professional operators were still calling the interface "likely to very likely" to trigger on high north-facing slopes with potential to size 3. The old saying on the Coast seems to be, "Give it a couple of days to settle-out and it should be fine". That may be true some of the time, but if you live by this rule you may also die by it as you'll be less likely to identify anomalous conditions such as the ones we're seeing now.

Travel Advice for the South Coast

Moving forward, the weak interface will strengthen. But before that happens, forecast warming may prolong the reactivity of the weakness as well as increase the probability of cornice fall (a likely trigger). If I were traveling in the mountains I would keep a few things in mind:

I would be alert to conditions that change with elevation. If you're climbing a route you might not encounter any significant buried persistent weaknesses until you reach about 2200m.
Before committing to a steep line, I would try to gain snowpack information from a safe representative slope.

It's a Wrap!

Hopefully this end of season blog post provides you with additional information that is intended to help mitigate risk when dealing with a persistent slab problem. I would understand that although spring can be a window for tackling big objectives, patience may be the key to shredding safely. The big exposed lines will be there in a few more weeks, or next year. It's easy to get sidetracked and forget about what is buried below.

Thanks again for another great winter season.

Spring Danger Ratings (Guest Post by Brad White)

Brad White — Tue, 02 April 2013 00:00:00

Every year it seems there's a debate of what to call the avalanche danger in the public bulletin when true spring conditions have arrived. For example: frozen solid and LOW danger in the mornings rising to wet and unstable HIGH or EXTREME conditions by late in the day, but there is only one forecast rating for the 24 hr. period. Should the rating default to the highest possible danger to warn people that avalanches are almost certain at some time in the day, or default to the lower end because travel while frozen has almost no avalanche danger, or pick somewhere in between?

At various times the terms "Variable", "Not Rated*(*see text, )," and "Spring" have been used to overcome this dilemma rather than pick a single rating, but this approach is not standardised to the North American Danger
Scale.

It's important to remember that avalanche danger varies both spatially (over terrain) and temporally (over time). We have no problem understanding that the danger may be different in different places in the terrain and can certainly think about danger improving or decreasing over time periods of several days. The issue with spring conditions is that the temporal swing in danger happens rapidly within the period of 24 hrs. normally covered by a public bulletin, (or a commercial operational forecast), so determining the specific danger is really is a question of timing and aspect.

When I am asked how the danger can be rated as "LOW" when there have been a number of large avalanches observed on a given day, I think about it this way: "Where in the terrain would it be possible to go and not be subjected to avalanche danger on that day, and how long during the day would it be possible?" (space and time). If there have been clear cold nights with a good solid freeze and the answer is that you could go almost anywhere and
have solid snow conditions and have them for a reasonable amount of time, then obviously the danger must be LOW. The bulletin user has to understand that timing is part of the equation. Conversely, if there was cloud cover,
very little freeze and there would likely be stability problems during the majority of the day, the danger would have to be higher.

"LOW DANGER" does not mean "NO AVALANCHES." It takes into account the fact that there is a swing in danger during the day and, that for the average bulletin user who can understand that ice melts when heated above zero, the conditions are excellent and it is the time to take advantage of the conditions.

This last week has been one of the best weeks of ski touring in the Rockies for some time. Excellent freezes with very little in the way of avalanche concerns and good travel. We use the headline to highlight the importance
of good timing, and give the users the "Green Brick." Go have some fun. It is the right time to do the big trips. Use your head, start early, keep an eye on the temperatures and the faces that are exposed to the sun and enjoy! Come home before the avalanches start... and the danger to you will be LOW.

Brad White - Parks Canada Visitor Safety Programs Specialist/Mountain Guide

Shooting Cracks, Whumphs, and Remote Triggering

ilya storm — Fri, 22 March 2013 00:00:00

Your avalanche risk management can improve with a better understanding of the mechanics going on under the snow's surface. Knowing how to change a transmission doesn't necessarily make you a better driver, but opening the hood to check the oil or fill the windshield washer is something every driver should know how to do.

Several close calls over the past week involved remotely triggered avalanches. Here's a bit of a backgrounder on what's going on and, more importantly, what to do about it.

You need two things for a slab of snow to release: failure in the weak layer and energy that drives the failure causing it to spread. In other words initiation and propagation. Initiation happens when the snowpack structure is overloaded, and a rider (whether on skis, board, or sled) is often that trigger. That's because we have a stress bulb that goes into the snowpack, it follows us around like an invisible shadow, and will trip the landmine if you go over it. If you're interested, a bit more info on stress-bulbs is available here. Propagation is the idea that a localized failure can spread, travelling along the weak layer like falling dominoes.

We need conditions that support both initiation & propagation for an avalanche. The good news is that often obvious clues give us great feedback that conditions are primed - if we know what we're looking at. The bad news is that sometimes there are no clues until it's too late. Here are three important billboards that nature provides:

Shooting Cracks: When snow fails like a cookie around your board, boots, or sled, but doesn't spread you have slabby snow, and you've met the first condition: initiation. If the crack shoots away from you (typically 5 to 20 metres) you have both initiation & propagation.

Whumphs: A whumph is a rapid settlement in the snow that feels and sounds just like the word - whooooomphhhh. Typically they happen when you're on gentle, open terrain, and if you look around sometimes you can see cracks on the surface at the edge of the collapsed slab. A whumph tells you there's initiation, propagation, and a defined slab that moved - in this case the snowpack simply collapsed or settled.

The difference between shooting cracks or whumphs, and avalanches is a single missing ingredient: terrain! Add some slope angle and instead of the slab moving a few cms (shooting cracks) or settling (whumph) you've triggered a real live avalanche. A whumph is an avalanche that tried, but couldn't.

Remote Triggers: Remotely triggered avalanches - when the avalanche releases at some distance away from the initiation point (where you tickled the weak layer) - is simply a whumph that continued travelling away from you out into avalanche terrain. With the right conditions you can remotely trigger avalanches 10's even 100's of metres away. That's a problem if you're at the bottom of a slope, less so if you're safely up on a ridge, and it's hard to control things in crowded areas where other groups are riding all around you. The problem with remote triggers, if you think of them as an important clue to help you understand current conditions, is that you're in the wrong place when the "ah ha" moment hits. The talk of the town last week (at least if you live in Terrace) was a remotely triggered large (size 3.5) avalanche that buried three skiers (all deeper than 1.5m). Incident report available here.

Managing your risk during times of remote triggering is challenging. Here are a few ideas to help:

Broaden your situational awareness to include not just where you are in the terrain, but where your buddies are, and what other groups near you are doing.
Avoid "thin spots" where triggering is more likely. Remotely triggering avalanches from thin wind-scoured ridges is common when conditions are right.
Evaluate terrain with an eye to its "connectiveness". By that I mean an awareness as to how
- avalanches can be triggered from adjacent terrain
- how avalanches can travel across typical terrain boundaries (like ribs, gulleys, or around small cliff bands) thereby linking terrain in a surprising way, and
- how groups in adjacent terrain may be relevant to you.
- Slopes with recent avalanche activity may be a good terrain choice - if the weak layer was removed and the hazard eliminated. Adjacent slopes that haven't slid may be the worst choice.
- Smaller, supported slopes with open, unconfined runout zones free of terrain traps may be a good choice of terrain.
- Regroup in safe spots. Possible locations include high ground, off to the side of avalanche paths, and well-away from the bottom of slopes. Big avalanches often run farther than we expect them to!

Throttle Back

James Floyer — Fri, 15 March 2013 09:00:00

If you're heading into the mountains this weekend, go cautiously and watch for the possibility of human-triggered avalanches. The snowpack is not yet trustworthy following the recent big storm. This applies whether you're sleddin', shreddin' or snowshoein'.

Pat on the Back

It's been a great season. You have to go back to 1980 to find a winter in Canada with an equally low number of fatality statistics for this point in the season. That's 33 years! And there are many times the number of recreationists using the mountains now compared to 33 years ago!

So let's give ourselves a pat on the back. Collectively, we're doing things right. Word has been going out when conditions are bad, and (for the most part) folks have been responding by making good terrain choices. When conditions have been good, folks have been hitting the higher/steeper/gnarlier lines and having a blast. It's helped that this year the distinction between good conditions and dangerous conditions has been fairly obvious. Still, a big part of this year's success has been due to the diligence and good decision making of the mountain user group.

Winter's Back

Actually, it was never over in the higher bowls where people like to go riding. Lower down, it feels more like spring. Or maybe more like a deluge. In many areas, the recent pineapple express dropped a tonne of rain in the valleys and a mix of rain and snow higher up.

It's what that new snow/rain is sitting on that has me a little worried. The recent weak layer from around March 10^th has been very reactive, with storm snow above this layer reported to be very easily triggered. At lower elevations, once things cool down and the rain-soaked snow freezes, I suspect this won't be much of an issue any more. Higher up, however, above the rain line, or where only a little rain fell, the new precipitation has simply added more load to the snow. This will have done little to stabilize the snowpack when we consider human triggers, but will have increased the potential size of any avalanche releases.

Folks looking to get their winter fix this weekend will be drawn to the higher bowls, to hunt down the good riding conditions. My advice is to travel cautiously and avoid big open lines. It's too soon after a big storm to trust the snowpack. Small slopes with friendly runouts (no terrain traps) and escape routes are a good choice. Larger slopes, particularly those with steep, convex sections, are best avoided for now.

I'd like to point out that professionals are very much still watching the touchy weak layer from around 12^th February. This weak layer was the suspected sliding layer associated with the two fatal avalanches in the second half of February. At higher elevations, I would consider this layer to be still in play in many regions. There is a very real chance a smaller avalanche triggered near the surface may step down to this deeper layer, dramatically increasing its size and destructive force.

Back to Basics

Just because you can see grass and crocuses in your yard doesn't mean you don't still need your full winter gear (including your transceiver, probe and shovel) for mountain travel. You also still need your avalanche brain in gear. Bear in mind that when conditions are changing rapidly, like they are at the moment, it becomes even more important to make your own observations to help assess snowpack stability. Be on the lookout for signs of instability. If you see recent avalanche activity, feel whumpfs, or see the snowpack start to crack at your feet or under your sled, you need to back off to more mellow terrain. Also, you need to consider the deeper instabilities. There are fewer observations you can make that will provide accurate information about this type of avalanche problem. The key is diligence, and a commitment to selecting smaller terrain that won't bite too hard if the snowpack lets you down.

We've got your Back

As always, keep checking the bulletins before you head out. We'll keep you apprised of the latest mountain conditions from our extensive network of observers. Also, make sure you talk to other mountain users from your area who you trust. And it may not be too late to take a course - there are still some providers offering Avalanche Skills Training (AST) courses in the second half of March and even into the first half of April for some regions.

Latest bulletins: http://www.avalanche.ca/cac/bulletins/latest

AST Courses: http://www.avalanche.ca/cac/training/ast/courses

James Floyer

Deep Persistent Slabs in the Yukon

YAA Field Technicians, Karl Klassen — Tue, 05 March 2013 16:00:00

A season plagued by bitterly cold temperatures, ferocious winds and a real lack of that 'white stuff' produced slim pickings for a majority of the season in the Yukon. Finally spring arrived! In February?

Since February 1^st, the Yukon has been unseasonably warm and the White Pass has received practically its entire snowfall from October through January over again, but in only one month!

Travel conditions for both skiing and sledding have drastically improved, as new snow and warm temperatures built a strong upper snowpack, and strengthen the mid-pack. Not to mention the mild temperatures and sunshine have made it much more enjoyable to actually head out into the backcountry. Finally, the skiing and sledding is actually really good right now as many of you who are reading this can probably attest too. However, (yes unfortunately there is a 'however') before you and comrades go chasing up to ski that gnarly couloir you have eyeing or teeing up that big 45-degree north-facing slope…there are a few things you should keep in mind.

We are dealing with a Persistent Deep Slab avalanche problem. Weak sugar snow (facets and depth hoar) created during the cold months of November and December exists at the bottom of the snowpack where you cannot see them.
Even though we have had a warm month of weather and the upper snowpack has transformed, that persistent weak layer near the ground has not; it's still weak and we have seen large, destructive natural and human triggered avalanches failing on this layer in the past two weeks.
Looking around last weekend, you'll likely have seen tracks on many different slopes with no consequence. Don't be lulled into a false sense of security. A lack of instability signs should not be mistaken for a sign of stability.
We are dealing with a low-probability/high-consequence type of avalanche. The chance of triggering one is low but if you do it'll probably be a big one and if caught, you're not going to be walking away from it.
As the weather improves into spring it is easy to be sucked into 'blue bird dreams' and summit goals where human factors and group dynamics begin influencing goals for the day.

Managing risk in low-probability-high consequence scenarios has a lot to do with discipline and risk tolerance. If you are willing to risk more, you'll ride more aggressively. If you prefer to hedge your bets, you need to be much more disciplined and conservative, even though people around you may be going for it without any apparent consequences.

Here's a few things you can do to reduce risk in low-probability/high-consequence scenarios:

Back off when weather factors add stress to the snowpack: new snow, rain, wind strong enough to drift snow, rapid warming or cooling due to air temperature changes, and strong solar radiation are all factors that can trigger deep persistent slabs.
Stay out from under cornices or slopes above where a cornice fall or smaller avalanche from higher up might trigger something bigger below.
Stay away from shallow snowpack areas.
Stay away from areas with variable depth snowpacks.
Never regroup in avalanche tracks or runouts: regroup only in safe spots such as dense trees, well out into flat ground, or on large, well-defined high points.
Remember that big, deep slabs can run much farther than expected. In some cases they will overrun traditional boundaries in avalanche tracks and runouts. What might be a safe spot in a small avalanche might not be in a big one like you get with deep persistent slabs.
Avoid terrain traps such as cliffs below, gullies, water features, and rapid transitions from steep to flat (e.g. road cutbanks, steep slopes running onto a lake.
Ride smaller slopes rather than bigger ones.
Ride lower angle terrain rather than steeper.

Some years, deep persistent slab problems stay around for months, even into the summer. Keep a watch on reports and forecasts for your region. It could be that some slopes might be high risk for the rest of the season and you may need to wait until a better winter to ride them if things don't get better this year.

You can read more about low-probability/high-consequence deep slab avalanche problems here:

http://www.avalanche.ca/cac/pre-trip-planning/decisionmaking (look for the "essentials" articles in the right sidebar)

http://www.avalanche.ca/cac/library/research-and-articles/snowpack (read the "Persistent Weak Layers" articles by Karl Klassen

Rescue Works - Sometimes

Ilya Storm — Mon, 25 February 2013 12:00:00

A few minutes ago I ran into a friend on the street who told me his riding buddies this weekend insisted on strapping their shovels to their sleds rather than sliding them into a pack. I responded with something like "I know the guy you need to ride with". Actually he's guy we ALL want to be our buddy when it counts. In fact, I think this guy deserves a medal.

Before you read his story, stand up from your armchair. This isn't a quarterback that deserves a thrashing from the comfort of your lazy-boy. The fact is, avalanches happen and they happen to good people, people who plan to come home to recount their adventure, people with avalanche training, skills, and experience. The reality is we can't forecast perfectly (it's a combination of science, reason, art, and intuition) and we can't manage our risk perfectly. This is precisely why rescue gear and training is a crucial final layer of defence. Transceiver - Probe - Shovel are the final arrows in your quiver when things go wrong. And you are the person with the bow shooting those arrows. So resist the temptation to criticize (they should've done this or that better) and give yourself a shake before deluding yourself into thinking it CAN'T happen to you.

Read this gentleman's account and tell me he isn't who you want on your side when you end up under the snow. Tell me he doesn't deserve a medal!

ilya storm

_________________________________________________

I was out front of the 2 of us, as I started side hilling Half way up a 30-35 degree slope witch gradually rolled off the top upwards of me with few small groups of medium sized trees. Downwards the sloped rolled out then dropped into a ravine. About 10-15m into the side hill I looked up and noticed the entire side of the hill started rippling and sliding. At that time all I though was get to safety my only option was to continue side hilling to safety, I found it about 50 m along the hill where a group of larger trees broke up the slide and have me protection from the slide. As I waited out the slide I lost track of the snow converted dirt bike riding with me. The slide about 20 seconds after I got to safely slowly came to a stop. I them immediately without hesitation rode to the bottom of the slide and closer to where my buddy would have been. Due to the loose snow on top of the already upwards of 30" of fresh powder, from the avi my machine sank to the running boards. I was about 30m down hill of where I last saw my buddy. With a small group of trees between me and where I last saw him. Without hesitation I dropped all my gear pulled out my tranceiver switched it to search and thank god I straight off the bat locked into his signal 15m uphill. I pulled my probe and shovel out of my bag and started moving as fast as I could In the conditions of snow past my hips. It was faster to crawl on top of the snow at this point, it hadn't settled yet. It took me about two minutes to get from my "safe spot" to my buried partner. My element transceiver let me straight above him with a reading of 1.8m below me. I took my probe and confirmed he was Down there stuck it in and nothing made the adrenaline kick in like sound of the probe hitting something hard Down there. At this point I had dropped my coat gloves and helmet on the way up the hill to prepare for the digging ahead. with my shovel already assembled I began digging and digging and digging soon to deep not to start standing in the hole next hip deep. With what seemed like forever I was well up to my chest expecting at this point not to be able to save him didn't seem to affect the speed at witch I was digging. As I began to throw up from over exertion bang ended up running right into his helmet with my shovel I dropped shovel and began using my hands to uncover his helmet the snow was hard as concrete that far down! I grabed his arm after uncovering a little farther to try and loosen his upper body his arm limp as a wet noodle the snow bot letting up he didnt even budge with all 240 lbs of me pulling on him. His face was looking upward I grabbed the shovel and jammed it into he snow above his chest digging the hole bigger. And bigger farther down to his torso. One final scoop and the suction was broken. And every bit of pressure pushing down on his lungs released and a huge gasp from my partner... I looked at his chest he was still not breathing.... At this point I had removed enough snow to perform CPR I worked on removing his helmet witch at this point I realized how cold my fingers were I had zero feeling in them. After working at it for a bit I just jamed my finger in the mechanism releasing the strap I quickly pulled his helmet off. I will never forget what I saw when I pulled his helmet off. Blue purple every colour a person should never be no pulse noticed visually or felt on the caroted artery Streight into CPR 2 breaths with jaw thrust 30 chest pumps 2 more breaths 30 more chest pumps, bam started breathing faintly I opened his airway using jaw thrust immediately air started moving through his mouth the blue purple skin was being replaced with red flush skin. I could see the caroted pulsating faintly then stronger and stronger still had no feeling in my hands so I could not use them to determine the pulse. In the bottom of a 6' deep hole nearly streight up all arround me. I continued to hold jaw thrust for he was struggling not to choke on his own tounge. Realizing we were not outa the woods yet I knew we needed help no cell phone service on my phone I checked the pockets of buddy his phone had no service. I was fucked still had a guy not fully breathing on his own and couldn't leave him for help and no service.... I had to wait a bit and hope he regained consciousness witch I wasn't even sure if he would. I had to reposition his head so he could breath on his own using my jacket I put it under his head. And put him in a head tilt chin lift position using my jacket to support his head. Clear breathing and in the recovery position legs and hips still trapped in the snow I hopped out of the hole I had dug. Finally able to catch my breath. Without leaving visual contact of my riding partner I held my phone up trying to get some cell phone service... Nothing. Out of the corner of my eye an arm came up finally some movement and a couple words " oohhh look at my snow fort" then out of it again. After a few times of signs of consciousness and movement a Few coherent words " where am I, what happened" lots of moaning. But regaining consciousness and quickly. Finally realized he had a radio and radioed out for help from the rest of our group huge relief. They heard us and knew where we were. 20 minutes later they showed up. After buddy was fully coherent and no further injuries and clear thoughts back to his head. Just before the rest of the group showed up I finished digging buddy out nearly an hour or digging I would imagine, his legs were concreted in with how long we had been Laying in the snow. While laying in the snow for so long buddy had gone hypothermic and was shaking quite a bit as was I not nearly as bad though. The group help warm buddy up and I put my gear back on to warm up. They dug his machine out witch was laying upside down right beside him. Helped me get my machine unstuck and we all rode out.

Changes

James Floyer — Wed, 20 February 2013 16:00:00

I'm writing this as a bit of an early heads up for the weekend and into next week. Conditions throughout western Canada, and particularly in the Columbia Mountains, are changing, and in many areas avalanche danger will be on the rise.

We've really been blessed through much of this season with generally stable snowpack conditions. Locally, I've skied terrain this year that during previous seasons I haven't remotely considered venturing into. I've talked to other skiers and sledders who have said similar things.

On Friday, it looks as though the snow tap will get turned back on again, with a series of storms lined up to bring winter back to the mountain regions. The storms will bring the "regular" danger elements associated with new snow loading, wind loading, cornice development etc… However, I'm also concerned with a buried weak layer that's already been responsible for a number of skier-trigged avalanches.

The story started around 12^th February, when a weak layer of surface hoar that had grown during the previous dry spell became buried by new snow. We've now seen a few storms drop sufficient snow on this layer for it to become reactive. There have been several skier-triggered avalanches, and one snowmobile incident reported to us from the Columbia Mountains in the last 2-3 days. While the official report is still in preparation, it is likely the fatal incident from east of Jumbo Mountain on Monday ran on this layer.

What we know about this layer is that it is widespread at treeline and alpine elevations. It has been reported to exist on all aspects. However, appears to be particularly reactive on southern aspects, where it may have been deposited on top of a sun crust.

While it's too early to say how long this problem will linger for, my fear is with additional load from Friday's storm, we're likely setting up for a fairly hazardous weekend. I don't see anything in the incoming weather helping to stabilize this layer out, and the additional new snow will make larger and more destructive avalanches more likely.

My advice would be to play things safe if you're heading out this weekend. It's not the day to go out and recklessly charge up (or down) the biggest slope on the mountain. It's the time to choose small, lower angled slopes with good runouts (no terrain traps). If you're a skier, you might decide it's best to stay in the trees (but be wary of steep open glades). As you're traveling, be aware of the possibility of remote triggering and avoid exposure from above. Bear in mind we've got used to dialing things up this season, but it's the ability to dial things back at the right time that keeps us safe.

James Floyer.

Heads Up For The Long Weekend - by Shannon Werner

Shannon — Fri, 08 February 2013 00:00:00

Wow! I can't believe it's already Feb 8th and the first BC Family Day Weekend, very exciting. Are you going to be out in the backcountry this weekend? I will be. The weather looks fantastic with blue sunny skies and a bunch of fresh powdery snow to indulge in. What a great opportunity to get out and play.

The main reason for this blog post is to encourage and remind recreational backcountry users to pay close attention to the Bulletins through the weekend period. So far this season we've been enjoying a fairly stable snowpack and folks have been highmarking, skiing big slopes and dropping into those completely awesome aesthetic lines with a high level degree of confidence. The backcountry has been getting schralped this year! There is nothing wrong with that, as long as your travel habits and use of terrain changes when the snowpack and avalanche characteristics change. It's important to maintain a diligent approach to terrain selection to best manage the current conditions.

So far, it's been an unusually quiet winter in terms of avalanche accidents. I'd really like to applaud you. I truly feel that backcountry recreationalists are becoming more engaged and involved with personal avalanche awareness and a skill set that will help them manage their risk and decisions while traveling in the mountains. I also believe with feedback from you, our users and support from our sponsors the Canadian Avalanche Center has been able to provide more products and tools to help you with this process. Whatever has happened, it seems to be working. We've seen a steady increase in the number of people taking Avalanche Skills Training courses and a steady increase of hits to our website, especially our bulletin page. Last year we saw 1.5 million site visits, which is fantastic. Every year we see more and more people going into the backcountry and so far this year (touch wood) no recreational avalanche fatalities yet.

So, when you jump into your vehicle tonight jam packed with your whole family and best buds, and you're headed to the mountains for the weekend here's a few thoughts to take with you on the road:

• Don't let your guard down, stay in tune with the public bulletin, ask around and gain local knowledge on current conditions in the area where you're headed.

• Keep in mind that the snowpack is dynamic and ever changing, which means you need to adjust your travel habits to match what's changed in the snowpack since the last time you were out there.

• Timing and intensity of the sun is tough to predict, but you can bank on it weakening the upper snowpack if it shines through.

• Persistent slab avalanche problems are tricky to manage and are currently easy to trigger by the weight of a skier or sledder. Good group management is essential.

• Be aware of overhead hazards like cornices and large slopes that may produce large avalanches running full path.

Considering that in years past we have seen an average of 14 fatalities a year, it's been a pretty remarkable season so far. I encourage everyone to keep it up, enjoy your day in the backcountry and come home for the après party. Have a great weekend and remember to keep your head and ski tips up out there.

Introducing cold snowpack to warm air

Grant — Sun, 13 January 2013 00:00:00

"Any rapid change in the mechanical or thermal energy state of the snowpack is a precursor to avalanching. And I emphasize rapid."

-Ed LaChapelle

It's important to know how we got to this point, here's a brief recap:

December brought consistent snowfall which gave us a great start to the winter. The snow shut down right around Christmas and then it went high and dry until January 4^th or so. During the high and dry period danger ratings were low and folks were able to ski and ride almost anything without risk of avalanches.

While folks were busy getting after it in the alpine, the surface of the snowpack was changing. We ended the high pressure period with small facets, surface hoar (up to 12mm) in sheltered treeline and below treeline areas and sun crust on steep south and west facing slopes. See Penny's January 11th blog post for more about what we do/don't know about this surface hoar

We opened the door to "zonal flow" on January 4^th. The mountainous regions of the province received 50 - 100cm of snow. We had a cycle of what we call "direct action" avalanches as the weak surface failed under the stress of its new load. Chatter amongst pros was full of avalanche observations and it was kind of a no brainer as to what was happening. Avalanche danger was high and slides were running naturally. Essentially the house was coming down.

Then it got cold as dry arctic air crept into the province. The big puffy jackets came out of closets from Vancouver to Revelstoke while our neighbors to the east laughed at how soft we interior folks are.

Activity on the January 4^th interface dropped way down as both time and temperature tightened up the snowpack. When you put things in the deep freeze, they have a tendency to do that.

There's been lots of slope testing this weekend in the form of explosive control work and recreationist getting after it. Most regions have dropped to Moderate at all elevation bands. Like Penny, I wish I was out there slaying it with all of you! But alas, these forecasts don't write themselves.

What's next?

Well, on Monday the ridge of high pressure shifts to the east which opens the door to a massive amount of warm air currently sitting off the coast of BC. As the warm air enters the province it will override the cold air presently in place. This should set the stage for inversions as cold air remains pooled in the valleys while warm air joy rides its way into the treeline and alpine. It looks like the boundary will be somewhere around 1000m. Below that, it will stay cold, above that, we could see ridge top temps as warm as +5. That's a 20° shift in temperature in a matter of hours!

If there's one thing to remember about snow, it's that it hates rapid changes. Atwater figured this out in 1954 and it remains a stalwart of avalanche forecasting.

An avalanche forecast is only as good as the weather forecast behind it. Right now, the best Meteorological brains in Canada tell us that we'll see an AFL, or "Above Freezing Layer" from about 1000m to 2500m. This warm air will first become a factor in Yukon and the North Coast late Sunday, creeping into the Northwest Inland Monday. It likely won't enter the airspace of the Columbias and central interior until Tuesday. With the wild topography of our great province, this warm air is going to get beat up and forced in directions we can't currently anticipate. Some areas will get it, some areas won't. In 10 years we'll probably all laugh at the rudimentary weather products we currently rely on, but that's the deal for now. The bottom line is that it's going to affect much of the province but we can't pin down the exact timing and intensity.

As an avalanche forecaster, I'm prone to turbo-geekyness, so I'll briefly touch on the mechanics of what I'm hypothesizing here. Essentially, I think that we're relatively poorly acquainted with the January 4^th interface. We think that it's mostly blown out of the Alpine, but I suspect there are still many slopes in the alpine that are harboring this weakness. We know that it's relatively widespread at and below treeline. When it's really cold, the pack tightens up. Creep slows way down and our stress bulbs (how deep your weight is getting into the snowpack) are relatively shallow. (See Ilya's blog on stress bulbs from earlier today.) When it warms up, creep is going to increase. That will put more strain on the weak layer as the upper snow begins to creep downhill that much faster. Natural avalanches are possible and a lot of terrain will be primed for triggering in the form of icefall/loose snow avalanche/ human interaction.

Many slopes slid during or just after the most recent storm, and those won't likely be a problem. It's the slopes that didn't slide that I'm worried about. (The bad news is that it may be hard to tell one from the other as wind and snow reloaded many slopes that actually did slide during the storm.)

I'm also concerned that many folks were out there crushing it this weekend and subsequently gaining a lot of confidence. It's appropriate that confidence with the current situation is good, but the situation that's coming down the pipes is ENTIRELY different

So, what can you do?

The change is going to be initiated by incoming solar radiation. The effects of temperature will lag just a bit behind. So, the important thing is to watch the sun. Slopes receiving direct solar in combination with the warm temps may become unstable surprisingly quickly. You're best served by dramatically reducing your exposure to avalanche terrain once it starts to heat up. Simple terrain without exposure to overhead hazard is going to be the best bet. In all honestly, the ski/sledding quality is going to go way down, and it might be time to pull the plug.

There's going to be an inversion in place which is tricky, because it will still be cold down low. So, if you're an ice climber who's shivering in the shadows, you need to think about how the bowl above you is being affected by the rapidly changing conditions.

Of course we won't actually know until it's happening. My guess is that it's the initial warming that will be the big issue, but it could easily be the sustained warming on the second day that initiates a cycle. The important thing is that you are aware that the situation is changing and the reality is that we're unsure about the timing. It's a period of great uncertainty and new you need to adjust your plans accordingly. Good luck!

Stress bulbs

Ilya — Sun, 13 January 2013 00:00:00

Imagine yourself riding a sunny slope. As you carve turns or take a little air your shadow follows your every move and there's no escaping it. Now imagine how you're affecting the snowpack with your weight as you carve, sidehill, or land big air. You add stress to the snow, and also following you, like a second shadow, is an invisible stress bulb below you. Your shadow's shape changes as your move depending on where the sun is and the shape of the snow surface. So too does the shape and intensity of your stress-bulb, depending on what you're doing and the snowpack structure below. We think, based on current snow science research, that our stress bulbs penetrate deeper in softer and warmer layers than through harder and colder slabs. In other words, all else being equal, forecast warming suggests that your stress bulb is more likely to tickle a weak layer in the days ahead. And here's the rub - the warming doesn't need to actually reach the weak layer. That weak layer can still be nice and cold; it's just the slab property that changed.

If you're keen on doing the snow geek thing, here's a recent research paper on how we stress the snowpack.

Are you looking forward to the weekend?

Penny — Fri, 11 January 2013 00:00:00

I know I am. The weather forecast looks great and there has been lots of new snow this week. Not to mention the fact that I've been cooped up in the office writing avalanche bulletins all week. In fact it's killing me, sitting here, looking out the window. I can't WAIT to get my skis on and feel the snow beneath my feet.

But, to be honest, I am starting to feel a bit worried. I am starting to worry about you - you, the unknown reader, who is sitting in front of your computer, feeling just like me. What if you don't realise the potential dangers?

This morning a colleague told me I was "such a mother". Fair enough. But we all need someone to look out for us every now and then.

Simply put, the snowpack is not like it was before. Before these last storms, you could pretty much go anywhere and do anything. Avalanche danger was 'good-to-go' LOW across most of the province for a prolonged period of time. That was the time to test out your turbo, or get your steep chute fix.

But things have changed, and it's not a simple scenario. The storm snow (up to a metre of it) landed on some weak old snow surfaces, including surface hoar. The touchy nature of this interface has been revealed by skiers remotely triggering avalanches, even in very low-angled terrain. In one case (in the North Columbia mountains), skiers remotely triggered an avalanche from 200 m away, which then sympathetically triggered five more avalanches, each up to size 2.

So we know we have a touchy surface hoar layer. The problem is we don't know exactly where it is and where it isn't. The distribution of the surface hoar is really complex. It's most likely to be found in sheltered areas at and below treeline. It's found in some part of every forecast region. It might be isolated to a few specific slopes in a few specific drainages, or it might be more widespread, but only time (and people like you testing out the slopes) will tell. We also don't know how long it will persist as a problem, but I'd say for sure that it'll last at least until the weekend, given its current reactivity.

The other tricky factor is that, by the weekend, the storm snow should have settled out and begun bonding reasonably well. You're unlikely to see a lot of new avalanches to give you clues about instabilities in the snowpack. Avalanche danger ratings will have come down. But, believe me, that surface hoar is still going to be lurking somewhere, and the result could be a surprisingly big avalanche on what might seem like a benign (e.g. low elevation, low angled) slope.

So, as a mother, I'd urge you to take a cautious approach to terrain as you venture back out into the mountains this weekend. Eye the slopes with suspicion. Keep your shovel handy. To have any confidence in your local snowpack, you'll need to dig often and test the interface of the new snow and the old surface. Don't commit to any slopes before you are confident that it's not a surface hoar trap. Oh, and make sure you don't forget your lunch.

Penny Goddard

Residual Risk

James Floyer — Tue, 25 December 2012 00:00:00

Yesterday, on Christmas Eve, there was an interesting avalanche that occurred just outside Fernie. This has got us talking in the forecaster office-I'll try to explain why.

The avalanche in question stepped down from a small pocket of shallow (20 cm) wind slab that was triggered intentionally by a skier, to release a very large (size 3) slab avalanche that was big enough to destroy several trees. The bed surface was one of two crusts present in the snowpack at that location, most likely the lower crust that formed at the beginning of November.

Avalanche Problems

The main thrust of the discussion has been over what kind of avalanche problems this points to (as opposed to over danger ratings, which were considerable in the alpine and moderate at treeline for the South Rockies for that day). Avalanche problems for the South Rockies were listed as "Storm Slab" and "Loose Dry". However, the avalanche above points to a deeper snowpack problem that could be labelled as "Deep Persistent Slab".

So, should we ring the bell as a result of this incident and start talking about Deep Persistent Slab and the possibility of large, destructive releases? As has been demonstrated, the potential is there. There are crusts in the snowpack to act as a sliding layer and likely sugary facets next to the crust in places. There is a cohesive slab in the upper snowpack, caused by the settling of the storm snow and recent strong winds.

However, at this point in time, there has been very little other evidence this problem is more than an anomalous event, formed by a magic combination of localized snowpack (wind effect near ridge, facets near rocks and above the crust) and terrain factors (southern aspect, shallow rocky terrain) and a perfect trigger point. People have been riding hard in the backcountry and this is the only event in the last week that can be firmly attributable to releasing on one of the lower crusts. While we acknowledge this kind of event is possible, we potentially do bulletin users a disservice if we constantly warn of imminent danger, when in actual reality, the possibility of such an incident is extremely low.

Emerging Trend?

Of course, there is the possibility this event points to an emerging trend. If this is the case, it might just serve as a precursor warning for similar events in the future. You can bet we've been scratching our heads pretty hard and asking around to see whether we think this is the case. At this point in time, we do not believe it does. We are still comfortable with the analysis that paints the lower crust as an isolated, stubborn problem that is generally difficult to trigger and only triggerable in very specific locations.

So for now, we're keeping the Deep Persistent Slab problem out of the South Rockies and Lizard Range bulletins. If you're smart though, you'll have read the snowpack description that points to this potential combination and you'll keep it at the back of your mind. And you'll avoid shallow, rocky, steep terrain, where facet/crust combinations are most easily triggered.

Residual Risk

You should also think about the notion of residual risk. This is the chance of an unexpected, surprise event happening, despite best attempts at analysing all the various risk factors involved. We manage residual risk by sticking to good travel habits: riding one at a time through avalanche terrain, thinking about escape routes that channel us away from the main body of a potential avalanche, always carrying a transceiver, probe and shovel and knowing how to use them, regrouping in safe spots well away from runout zones, having good communication strategies… the list goes on. We can't eliminate all aspects of risk from our sport, but with thought, preparation and good current knowledge of the snowpack, we can bring the risk down to an acceptably low level.

James Floyer
(Avalanche size edited Dec-26-2012)

Southern Regions (and elsewhere): Stick to the powder

Thu, 20 December 2012 00:00:00

I love my job! Being an avalanche forecaster may not earn you the big bucks, but it sure has a load of other good things going for it. I guess one of those good things must be the opportunity to offer advice, otherwise I wouldn't relish the job as much as I do. Sometimes the most sensible advice just makes me want to smile-now is one of those times!

Stick to the powder

In many parts of western Canada, but especially in the south near the Canadian/US border, we've had near continual stream of light, fluffy powder snow since early December. The riding has been excellent and people have been loving it!

However, things are slated to change a little with the next couple of storms, due to our old arch-enemy of powder conditions-the wind. There's a lot of snow available for wind transport right now, and once the winds start to increase, this loose snow will be picked up and deposited onto lee (downwind) slopes in many exposed areas. It's in these areas where wind slabs, and hence higher avalanche danger, are most likely to be found.

The good news is that you really don't need to go to exposed alpine areas to get great riding right now. Sticking to more sheltered areas at slightly lower elevations will give you the best of all worlds: you'll get powder snow, you won't get your face blown off by the wind and you'll avoid much of the avalanche danger associated with wind slab development.

Staying at slightly lower elevation also plays well for the short solstice days (unlike the Mayans, we believe the days will get longer again) and the state of tuning of early season legs/arms/lungs/machines.

Sounds simple, and obvious, but sticking to the powder is really the best advice I can give right now.

Watch the temperature - make sure it stays cold

So far, the temperature has stayed cold, which is why the snow has been so light. For the most part, it looks like things will stay that way, due to a big arctic air mass affecting the majority of western Canada.

However, there are a few places in the south that may experience slightly warmer conditions on Thursday, Friday and through the weekend. These same areas also have the potential to see some locally heavy snow amounts, due to warmer southern air rising up over the cold arctic air below. In these places, you may see denser snow forming a slab on top of lower density snow below (which we call "upside down" snowpack conditions). These conditions can increase the avalanche danger on steep, open slopes. Unusually, the warmest air may be at higher elevations (as the cold, arctic air hugs the valley bottoms). This means you're most likely to experience an upside down snowpack in the alpine (where it's also windiest) or near the top of treeline.

The places most likely to see this kind of problem develop are: the Lizard Range near Fernie, Kootenay Pass between Salmo and Creston and the Flathead Range including Harvey Pass southeast of Fernie.

Once again, there is a convenient option for dealing with this: you don't need to travel too high to find the best riding conditions. Aim for upper below treeline (say 1600-1800 m), or lower treeline elevations and you should find cold, powdery, right-side-up conditions. If you do start to feel the surface snow becoming denser, consider backing off onto shallower terrain and don't expose yourself to avalanche hazard from above.

Holiday turns

Just a word to those who haven't had the luxury of riding the bottomless powder of the last couple of weeks yet, but who are relishing chance to do so during the holiday season:

Go out with a little bit of caution, ease into things gently, and check to make sure you're riding powder and not wind slab. Conditions may not be quite as good as the Facebook photos you've been seeing from your ski/sled bum friends absolutely everywhere on the mountain. But I suspect you'll find good (and safe) conditions out there if you pay attention to the snow and avy conditions, and stick to the powder.

James Floyer

Photo for North Columbia Cariboos Bulletin Nov. 23, 2012

Fri, 23 November 2012 00:00:00

Where is the Danger Rating?

T Riley — Tue, 20 November 2012 00:00:00

Producing avalanche forecasts and issuing danger ratings requires information. We rely largely on data from professionals and at this time of year, a lot of them have not yet started their winter operations. As a result, in the early season, we often do not have enough information to issue a full slate of danger ratings and other parts of the forecasts may be more a general overview than a specific description of the conditions. . For the next while, until our data flow is well established, some regions may only have danger ratings for some elevation bands. Some regions may have so much variability at this time of year that it is not possible to give a general regional rating. We may feel that we have enough information to describe the avalanche problems at higher elevations in regions where there's little variability.

A common early season problem is the variability in the "Below Tree-Line" or BTL elevation band. The upper BTL may have close to a metre of snow on the ground, and then it may taper down to nothing (below threshold) in a few hundred metres of elevation loss. The freezing levels bounce up and down from warm wet storms to cool dry breaks, and you head out for your day not even knowing how high you are going to drive before you launch the sled or snap into your bindings. How would you use a danger rating to help reduce your risk in this scenario? Can we assume that you are just travelling through most of the variability on a well-defined access road, or are you tearing into the first pockets of snow that you see to try to get some snow on your rad (or your rad on some snow)?

We would like to see you "dig down" past the danger ratings and colors at least as far as the avalanche problems. The avalanche problems are made up of an "avalanche character", some information about where we think you will find that type of avalanche (elevation and aspect), and what to expect as far as size and likelihood. This is where you should develop a mental picture that you can compare to what you find when you get into the backcountry.

Remember that the bulletins are designed to be a starting point for analysing risk and choosing trips that have terrain that matches the forecasted conditions. You should be updating the local danger on a slope or basin scale as you gather information during your trip. Using a tool like the Slope Evaluation Card in the Avaluator or the Decision Making in Avalanche Terrain Fieldbook can help you decide how much risk you are willing to accept, and adjust that risk by choosing the terrain that you travel through.

We don't know what you are planning to do, or where you are planning to go. We can tell you what kinds of avalanche problems we think you should expect based on what we know has already happened, combined with what we are expecting to happen in the next few days. It is up to you to get some training so that you know what to look for during your trip. Check out some training here.

AS we obtain more information, we'll add danger ratings to elevation bands and regions, avalanche problems will become more detailed, and the forecasts will be fully fleshed out. We hope you get in the habit of looking at the avalanche problems and develop your understanding of how the problems drive the danger ratings. Take it easy out there and start building your knowledge of the local snowpack. If you see something worth sharing, send us an email.

Shaking off the dust

Tue, 16 October 2012 00:00:00

It's early season in the mountains of western Canada and people are already riding hard. Rumour has it there's over a metre of snow in parts of the Columbias and up and down the Coast Range of BC. Hearing tales of folks riding through 40 cm of powder is great fun, but should also be a prompt to start thinking about avalanches.

The purpose of this, our first blog post of the season, is to help folks "shake the dust off," and begin to think about avalanche hazard before heading out the door for the season's initial foray.

One thing we notice about the early winter is people tend to go high. This makes sense: the snow falls first in the alpine and there may even be left over patches of snow or glaciers to help cover the ground. The problem is these are also the spots where you're most likely to encounter avalanche hazard.

Wind and storm slabs will form readily in alpine bowls and around ridgelines. They will be poorly bonded to the layers below, during and immediately following a storm. The weakness will be more pronounced and last for longer in areas where the new slabs overlie last year's snow, or glacial ice.

If you're heading out at this time, try to get as much information about conditions before you travel. Avalanche bulletins don't go live until the week of November 20th, so you'll have to be your own forecaster for now:

Talk to people who have been out recently.

Preferably talk to experienced riders who have ridden near to where you're going in the last couple of days. Did they see any avalanche activity? Did the snow surface feel dense with cracks shooting out from your skis? Did it have a loose, weak layer near the ground? Were they spooked?

Keep track of the weather.

Danger is often highest during and immediately after a storm. Give the snowpack time to settle. Ride mellower terrain if the weather has recently been stormy.

Know what's under the snow you're riding on.

Riding on steep terrain where a fresh slab overlies last year's old snow or glacial ice carries additional risk.

Early season avalanches at any elevation have the potential to be particularly nasty as rocks, slash, deadfall, stumps, etc. usually litter the runout zones. Even a small avalanche that pulls you over and/or through an obstacle course like this can be deadly serious.

The fact is a great deal of the mountains in the early season look good from afar, but are far from good. This is a great time to start practicing with rescue gear in non-avalanche terrain. Remember everyone in the backcountry should be equipped with an avalanche transceiver, probe & shovel. Furthermore, you need to know how to use it. What better time to practice than now?

As temps begin to drop the water ice climbing scene roars back to life. If hacking at frozen waterfalls is your thing, don't discount the avalanche terrain you can't see. Many ice climbs are underneath high elevation start zones that aren't visible when you're actually on the climb. Ice climbers need to carefully evaluate each slope for its avalanche potential. New snow and wind can quickly create unmanageable avalanches for an activity where anything more substantial than a little spindrift is unacceptable.

In summary remember the old timey words of wisdom, "If there's enough snow to ride, there's enough snow to slide." Be your own forecaster, approach the mountains cautiously and repeat the mantra of the early season; "Go Small!"

Prepared by Grant Helgeson and James Floyer.