Anthracites Playground 2-11-24

[goldenboy]

Might as well have a thread here in addition to the thread on the main forum https://www.tetongravity.com/forums/...67#post7025967

CB News: https://crestedbuttenews.com/2024/02...anche-sunday/?

[SILENCER]

This one has been harder than most to read about, understanding how many of you all knew him well...the proximity of this tragedy is too close for comfort even though I never had the pleasure of meeting him.

[powdork]

They have updated the accident summary this morning with newer pics. Full report out later in the week
https://classic.avalanche.state.co.u...=863&accfm=rep

[andy m]

The CAIC final report has been released:
https://classic.avalanche.state.co.u...=863&accfm=inv

[teleee]

The CAIC final report has been released:
https://classic.avalanche.state.co.u...=863&accfm=inv

FUCK! That is a rough read.


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[SKIP IN7RO]

signs, signs, everywhere there's signs

[Darren Jakal]

FUCK! That is a rough read.


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Rip in Peace Eric Freson, and condolences to friends and family.

“The avalanche broke approximately 30 feet above Skier 3 and quickly swept him off his feet. The group below watched as Skier 3 deployed his airbag and was swept over the cliff band and onto the broad, open slope below. The initial avalanche triggered a second, larger avalanche on the open slope. This second avalanche added substantial volume to the flowing debris. He went out of view of the group.
The avalanche ran into trees below the open slope, taking Skier 3 for a violent ride. The impact ripped the airbag from his body. Skier 3 came to rest, fully buried about 500 vertical feet below where he triggered the initial avalanche.”

That is a rough read, and troubling on many levels.

[kw_cap]

Truly rough

In the report there is the mention that while skinning one in the group found the snowpack shallower than expected, can someone explain why that's a red flag?

[MakersTeleMark]

Truly rough

In the report there is the mention that while skinning one in the group found the snowpack shallower than expected, can someone explain why that's a red flag?

Because it makes it much easier to trigger a PWL.

[cravenmorhead]

...and because they were depending on a deeper snowpack in the zone to mitigate the PWL danger.

[kw_cap]

...and because they were depending on a deeper snowpack in the zone to mitigate the PWL danger.

Got it, appreciate the explanation!

[Bunion 2020]

...and because they were depending on a deeper snowpack in the zone to mitigate the PWL danger.

I really have to question that line of thinking as extremely wishful.

Avalanches are one of the most powerful natural occurrences — capable of wiping entire towns off the map — and typically associated with large amounts of snow. This year, the lack of snow is record-breaking, but avalanche risk remains stubbornly high.

The Gallatin National Forest Avalanche Center reported on Feb. 21 that large avalanches and other signs of snowpack instability are continuing with “alarming regularity.” Avalanche experts say this season is unprecedented in persistent avalanche danger, despite a low snowpack.

Avalanche danger is ranked “considerable” across all areas in the GNFAC’s coverage, and has remained in that range or “high” since the first week of February, according to the organization’s weather and avalanche log.


In fact, very few reports since December have labeled any area as “low” in danger.

“Stepping into backcountry avalanche terrain (slopes steeper than 30 degrees) anywhere in the advisory area is like stepping onto the casino floor with the odds stacked against you. You might win a hand or two, but you’ll likely lose in the long run,” forecaster Dave Zinn wrote in Wednesday’s report.

Normally, GNFAC director and forecaster Doug Chabot said, instability directly follows after snowfall before stabilizing after a few days. This season, however, the GNFAC is having to hold avalanche danger higher than they have in years because the snowpack is just not stabilizing.

“A small storm has been enough to spike the avalanche danger to where we are seeing lots and lots of avalanches with a minimal amount of snowfall, that’s unprecedented,” Chabot said.

The problem with this year’s snowpack is that the early season snowstorms stayed on the ground without being buried and turned into sugary, faceted layers which never strengthened, Chabot said.

When layers remain weak but have snow fall on top of them, the risk of dry slab avalanches — the type of avalanche experts are most concerned with — are more likely.

Karl Birkeland, an avalanche scientist and former director of the National Avalanche Center, said while the average person might think less snow means less avalanches, to a forecaster or snow scientist, it’s a red flag.

Dry slab avalanches are caused by continued snowfall accumulating on top of weak layers prone to collapse. Extreme cold, like the snap in mid-January can also contribute to these persistent weak layers, named as such because Birkeland said they stick around longer than anticipated, extending avalanche danger long after new snowfall.

People are still triggering avalanches days and even weeks out from new snowfall, Birkeland said.

He said this creates dangerous situations because skiers and riders tend to believe that they can wait a few days after snow, then go ski avalanche terrain.

“This is the kind of season where you really have to recalibrate and understand that this season is different than our average season,” Birkeland said. “You need extra margin of safety in order to make it through a season like this.”

Birkeland said this season is one of, if not the worst, snowpack he has seen in the 35 years he’s lived in Montana.

“If you’re not paying attention to the avalanche forecast, you might think it’s like any other year,” Chabot said.

In the past 10 days, dozens of natural avalanches and several skier avalanches have been triggered. On resulted in a partial burial of a skier slightly northwest of Yellowstone National Park.

In the GNFAC’s Feb. 20 report, Chabot wrote, “the mountains have been talking to us... The translation is easy; she’s telling us the snowpack is dangerous.”

He reported that fellow forecaster Dave Zinn encountered a large collapse near Cooke City — after safely ascending the slope and conducting a safety test on the snowpack. The report said if the slope had been even slightly steeper it might have slid.

Chabot emphasized that despite their name, stability tested are actually “instability tests” to be used to detect signs of avalanche potential when there are not already so many naturally occurring ones.

“Right now, we don’t need them. We’re seeing whumpfs and cracks and cracking and avalanches all the time,” he said. “That trumps a stability test.”

Chabot added that the coming weekend and week’s warmer temperatures might see more skier and rider traffic, increasing the potential for human-triggered slides on the already precarious snowpack.

People need to be careful, he said.

While Chabot said apart from rain or melting, nothing could totally rectify the situation, two opposite events could alleviate it — either a significant snowstorm or a complete dearth of snowfall.

“We’ve been talking about that happening ever since Dec. 1,” Chabot said. “We’ve been saying ‘well once it snows and we get that big snowstorm, it will really help.’ And here we are, at the end of February and we’re still kind of waiting for that big snowstorm.”

As for the no snow option, Chabot said while that would help stabilize the snowpack, it would also negate the whole reason why people go out into the backcountry — to have fun skiing powder.

It is unclear if this year’s sustained avalanche risk without minimal snow is just an anomaly fed by El Niño weather patterns, but Birkeland said in general a changing climate will make predicting avalanche danger more difficult going forward.

Because avalanches are driven by the weather patterns of any given season rather than larger climatic patterns, the scientific certainty on warming winters is less certain when it comes to predicting future avalanches seasons, he said.

For instance, Birkeland said if average temperatures increase and come with more rain, and less snow, there may be fewer avalanches. But a season with more temperature extremes and big storms on top of a thinner snowpack might see worse conditions.

“I think the biggest thing that we can say about avalanches in the future is that things are going to be different. Typically, we try to predict what’s going to happen in the future based on what we’ve observed in the past and the thing that’s going to be challenging for us with avalanches is that we are probably going to see things in the future that we haven’t seen before,” Birkeland said. “So, relying just on our past experience is going to be more challenging.”

[whipski]

Heuristic thinking and biases

[Bunion 2020]

^^^ Dig dig ding!

[MagnificentUnicorn]

So many red flags.


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[cravenmorhead]

I really have to question that line of thinking as extremely wishful.

I agree. I think it's notably from a decision-making standpoint though, since the field observations weren't matching up with the conditions the team expected.

[Bunion 2020]

Really shitty to read this as well as the thread on the main page. Sounded like a well liked person who will be greatly missed.

I am shocked that we have not lost anyone around here this year. Snow pack is as rotten as the SJs and people are numb to the dangers and getting after it.

[Lindahl]

I really have to question that line of thinking as extremely wishful.

We basically always have that layer in Colorado. What happens is eventually it gets buried deep enough that the midpack bridges the layer and you can ski avalanche terrain again if you have history with the region and know what it takes to bridge and have been keeping an eye on pack depth. A storm can reactivate it though by being too much load for the midpack to bridge.

It sounds like they were counting on the midpack bridge. But perhaps what they didn't take into account was the surface hoar PWL (which they should have considered given the avy report), which we don't commonly see and is much easier to activate since it was right in the middle of the midpack and wasn't being bridged. It's not clear to me if it stepped down to the depth hoar or only slid on the surface hoar, but I think the latter.

Due to the surface hoar, and how unpredictable it can be in terms of location, I've been playing it pretty safe after it formed. Though before it formed, our depth hoar was so bad this year there really wasn't a good window where the midpack was bridging the depth hoar, so I've had to treat this year much more conservatively than I do most years. Local knowledge might allow you to step out, since if you were out a lot you'd know where the surface hoar formed and where it didn't, but with 2 young kids at home, I'm pretty out of touch. Anyway, that sums up how I'm looking at this year compares to others, and why I think they made the decisions they did, despite the typical depth hoar PWL that we always get.

Note: some people don't like the midpack bridge 'gamble', but in my experience, it's been pretty predictable, as we've experimented a lot with it over the years in our go-to zone, picking low consequence slopes or test slopes to learn more about what it takes to bridge and to learn what the factors are when it doesn't and even how it reactivates (2013 LL pass slide that killed several comes to mind). I don't think this works well universally across Colorado, but in areas with unusually high snowfall, like the Keblar Pass region, it can be done (in my experience).

[Bunion 2020]

Or so far you have been lucky. Different strokes and all that.

Thx

[MagnificentUnicorn]

We basically always have that layer in Colorado. What happens is eventually it gets buried deep enough that the midpack bridges the layer and you can ski avalanche terrain again if you have history with the region and know what it takes to bridge and have been keeping an eye on pack depth. A storm can reactivate it though by being too much load for the midpack to bridge.

It sounds like they were counting on the midpack bridge. But perhaps what they didn't take into account was the surface hoar PWL (which they should have considered given the avy report), which we don't commonly see and is much easier to activate since it was right in the middle of the midpack and wasn't being bridged. It's not clear to me if it stepped down to the depth hoar or only slid on the surface hoar, but I think the latter.

Due to the surface hoar, and how unpredictable it can be in terms of location, I've been playing it pretty safe after it formed. Though before it formed, our depth hoar was so bad this year there really wasn't a good window where the midpack was bridging the depth hoar, so I've had to treat this year much more conservatively than I do most years. Local knowledge might allow you to step out, since if you were out a lot you'd know where the surface hoar formed and where it didn't, but with 2 young kids at home, I'm pretty out of touch. Anyway, that sums up how I'm looking at this year compares to others, and why I think they made the decisions they did, despite the typical depth hoar PWL that we always get.

Note: some people don't like the midpack bridge 'gamble', but in my experience, it's been pretty predictable, as we've experimented a lot with it over the years in our go-to zone, picking low consequence slopes or test slopes to learn more about what it takes to bridge and to learn what the factors are when it doesn't and even how it reactivates (2013 LL pass slide that killed several comes to mind). I don't think this works well universally across Colorado, but in areas with unusually high snowfall, like the Keblar Pass region, it can be done (in my experience).

None of that really matters if they were triggering avalanches remotely and directly immediately before the fatal slide, no?


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[Darren Jakal]

If you are going to roll the dice with a propagating PWL in the mid pack (surface hoar) that could potentially step down to a depth hoar PWL then your terrain choice needs to be carefully considered. Not all avalanches are killers, but some are and an airbag, Avalung or companion rescue will be of no use.

[MagnificentUnicorn]

^^^The objective hazard on that terrain would give me pause with a consolidated spring snow pack


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[Darren Jakal]

^^^The objective hazard on that terrain would give me pause with a consolidated spring snow pack



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100% agree with you. The write up and especially the pictures of terrain and snowpack made me shake my head.

[Lindahl]

None of that really matters if they were triggering avalanches remotely and directly immediately before the fatal slide, no?


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From what I understand, the remote trigger slides were a southern aspect? We see activity all the time this time of year on solar aspects in our local terrain that have no relation to the stability of northern aspects in trees. Maybe they thought the same?

As for the direct, it was a small soft slab (it stepped down but they couldn't see that). Probably a pocket release with no real propagation potential that doesn't have unpredictable PWL characteristics. Not saying I'd make the same terrain choice (surface hoar only a few feet buried is not something I'd gamble with), but I can see how they continued if they weren't thinking about or aware of the SH problem.

[Foggy_Goggles]

Maybe chill a bit on the assumptions. It was a tragic accident. Mistakes were made. People are grieving.

Be humble. Learn. Thanks