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06/29/17, 08:57 AM

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Author Topic: March 19, 2017, cross post from NWAC obs  (Read 7067 times)
Charlie Hagedorn
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March 19, 2017, cross post from NWAC obs
« on: 03/20/17, 11:49 AM »

The poster there hasn't posted here, and I suspect TAYers will be interested:

http://www.nwac.us/observations/pk/710/
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Jason4
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Re: March 19, 2017, cross post from NWAC obs
« Reply #1 on: 03/20/17, 03:23 PM »

That would have been incredible to see and terrifying to be below.  I'm thankful they made it out ok and shared the observation.
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cumulus
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Re: March 19, 2017, cross post from NWAC obs
« Reply #2 on: 03/20/17, 08:56 PM »

Thanks for the link Charlie!  And thanks to whoever posted that. That's valuable info (and scary ..and lucky!)

Would be interesting to know what the running surface is with "the crown fracture face between 7'-25' tall." It's leeward, so more rapid build up, but with depth like that seems it would pre-date this last rain cycle...
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Stefan
Aleksey
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Re: March 19, 2017, cross post from NWAC obs
« Reply #3 on: 03/20/17, 10:31 PM »

Thanks for the link Charlie!  And thanks to whoever posted that. That's valuable info (and scary ..and lucky!)

Would be interesting to know what the running surface is with "the crown fracture face between 7'-25' tall." It's leeward, so more rapid build up, but with depth like that seems it would pre-date this last rain cycle...
agreed.... and a worthwhile observation for us to think on. must have been quite a cornice, and what a story that tells about regional n facing aspects!
i wonder what that vicinity will look like when the temps start peaking with the inevitable high pressures coming.
one of my favorite and most frequented hwy20 spots, was loosely considering a tour there this weekend but was held up at home.
really eerie feeling looking at those pictures
thanks for cross post charlie h, i might have missed that otherwise
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Lowell_Skoog
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Re: March 19, 2017, cross post from NWAC obs
« Reply #4 on: 03/20/17, 10:41 PM »

"March 2017 Low Probability-High Consequence Avalanche Cycle"

http://www.avalanche.ca/blogs/novemberfacetsmarchlphccycle
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Aleksey
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Re: March 19, 2017, cross post from NWAC obs
« Reply #5 on: 03/20/17, 11:43 PM »

"March 2017 Low Probability-High Consequence Avalanche Cycle"

http://www.avalanche.ca/blogs/novemberfacetsmarchlphccycle

thanks for the link Lowell

was in AK for most of winter and suddenly feeling very out of touch with the snowpack.
is your take that this is the same layering problem as whats described in the avalance.ca link?

from above...

"These were the building blocks for what is now called the “November persistent weak layer.” As the winter progressed, colder-than-normal temperatures and below-normal snowfalls eventually transformed that wet November snow into a weak, sugary layer of facets and depth hoar crystals. This persistent weak layer (PWL) is typical of its kind and has remained notably weak and of concern throughout the winter in many regions of BC and Alberta.

While early season facets and depth hoar are normal in the cold, dry climate of the Rocky Mountains, this season the November PWL is worse than usual there. It has also formed in the Columbia and Coast Mountains, places where this kind of layer is less common. Over the winter the snowpack has built up over this weak layer, creating a fundamentally unstable structure."

from the nwac report describing "an icy bed surface" my guess is that this is february record storms running on an old "warm front rain turned ice rink" layer, rather than a depth hoar issue i would guess that depth hoar would have had some time to compress under the weight of this snowpack.

curious as to your take on it

would be good to hear what experienced bc travelers who, unlike me, spent the season here think. very much appreciate the input, was planning a couple jaunts in that neighborhood
« Last Edit: 03/21/17, 12:19 AM by Aleksey » Logged
lefty72
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Re: March 19, 2017, cross post from NWAC obs
« Reply #6 on: 03/21/17, 06:30 PM »

I am just stalking this discussion from California.  It seems like based on this report from Canada, the event on Ruby, an earlier massive avalanche in the Pemberton area after a skier cornice cut, and finally the number of accidents posted on NWAC in the first few days of March there is a chance that something is of concern in the snowpack in the PACNW.  Seems like an interesting thread worth being aware of and perhaps included in the avalanche forecast from NWAC.  Interesting and productive discussion.  Always learning.
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RonL
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Re: March 19, 2017, cross post from NWAC obs
« Reply #7 on: 03/21/17, 07:58 PM »

It is a rare skier who would dig 7'. If someone were to do this would the layer be identifiable? Send out the pro observers for some excercise? I would be interested in how to incorporate these clues into plans for the weekend.
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Aleksey
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Re: March 19, 2017, cross post from NWAC obs
« Reply #8 on: 03/21/17, 09:33 PM »

It is a rare skier who would dig 7'. If someone were to do this would the layer be identifiable? Send out the pro observers for some excercise? I would be interested in how to incorporate these clues into plans for the weekend.

unarguable. just seems like a bit of a pattern building. knowing about this event makes me:

1) extra weary of travel beneath cornices. after this....i wont be under one in that neighborhood for a while. not usually this cautious by any stretch.
2)especially on a n facing/leeward aspect in the same vicinity.

and with the empirical evidence showing the reactivity of slides of this magnitude....i will also be avoiding valley floors well below such aspects, especially after storms or during a warming trend

anyway, glad this got written up, i was almost there myself and have zero doubt I would have been skiing it. its just seems like with all the HUGE slides being reported along the hwy20 corridor that this is in the upper range of LOW probability.
so as far as weekend plans? me personally id search for proto corn on rainier s side rather than n facing pow along n cascades if the temps spike during the tour. i may have chosen otherwise prior to reading that
youre right though Ron, hard (impossible for me, id have to admit) to predict and avoid such a thing, especially if no reports clue anyone to the potentiality
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cumulus
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Re: March 19, 2017, cross post from NWAC obs
« Reply #9 on: 03/21/17, 10:51 PM »

Good points Aleksey.

There's a lot of warmth and precip saturation in the snowpack this week (again!), at least at the mid elevations (4-5K), with a cooling trend for the weekend. May take some time for that cooling to solidify things though, and the cooling looks to be temporary. May be good... hard to say from here. I wouldn't count on corn on Rainier though... looks like 2' of new between now and then.

the number of accidents posted on NWAC in the first few days of March there is a chance that something is of concern in the snowpack in the PACNW. 

Early March incidents were from topical layers... i.e. new snow that started as powder but then got upended by rain, cooled down again with more new snow on top but altogether hadn't entirely cohered... with some wind slab thrown in for good measure. Entirely different from the deep low-prob/high-consequence scenario on Ruby (and as described by in the canadian Klassen write up). A somewhat enigmatic beast...
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Stefan
garyabrill
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Re: March 19, 2017, cross post from NWAC obs
« Reply #10 on: 03/22/17, 06:48 AM »

There are several messages in the Karl Klassen message that resonate not only in the recent Ruby event but also with respect to the current state of the snowpack. The most obvious is the concept of dealing with high consequence avalanche situations. The methodology that he suggests in describing what he would do is the take home point. And the points he makes are relevant here now even if the snowpacks are different. The common thread is that when there is the prospect/potential of major slides, trying to evaluate probability based on snowpack evaluation is essentially a fools errand. It is enough to know that there is a possibility not near "0" that a big slide could happen. Depending on individual risk tolerance one can choose to take that risk or not. But in the interest of longevity it is important to realize that if a slide occurs the likelihood of fatality is the expected consequence. If a large enough group of people take that risk with what is right now far from near "0" probability, it is basically a lottery. Or a comparative analogy would be to bet all of your money on the Seahawks because you are sure they are going to win.

In the Rockies the problem is as described by Klassen, obviously. Here the problem is the very large amount of new snow especially at elevation since late February coupled with winds in many of the storms. Even if one is "sure" that an avalanche will not step down or otherwise be released, there is a lot of snow above some elevation.....perhaps in the North Cascades best represented by a review of the Mt. Baker 5000' telemetry. A quick review of Friday's NWAC forecast talked specifically about 2-4" of rain being received in 24 hours. Although in the ski areas much of this fell as rain, at high elevations this was clearly not the case (telemetry). There was, even assuming (questionable assumption) that an avalanche would not or could not ultimately involve snow layers down to the mid-February crust, the risk of very big slides.

You don't need to do a snow profile to understand the nature of this risk. You will get good exercise in digging such a snow pit but that is about all. In the long run safety is about the risk profile one is willing to own. Potential big consequences should make one re-evaluate one's long term risk profile.

Incidentally, NWAC is discussing how to get out the message of Karl Klassen because of it's current applicability.
« Last Edit: 03/22/17, 06:52 AM by garyabrill » Logged
RonL
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Re: March 19, 2017, cross post from NWAC obs
« Reply #11 on: 03/22/17, 08:02 AM »

Thanks Gary. I think you have summed up pretty well what points NWac might put in a warning. Others mentioned north slopes being a greater risk. If that is the case they might get more specific that way. As far as incorporating it in my own planning I will likely stay off bigger exposures a while longer this spring.

Kidding aside though, when these deep buried pwl are an issue, I do wonder at how they appear when exposed. I have looked at obvious ones in old slide paths and a long time ago I dug a deep pit to locate a pwl that was an issue, but my snow science skills aren't keen enuf to really differentiate why that layer was a problem vs other old storm layers.

I think it would be interesting to learn more from someone with the skills which specific part of the snowpack slid and how big the cornice must have been to trigger that. It's mostly curiosity but a better ability to work out what's happening could be useful as well. I like that you separated for us the local events from the Colorado discussion. Too often these discussion default to describing a pwl in our snowpack as "Colorado like" as though that sums it up.

It may exist some where that I am not aware of already but I have felt that a missing piece of a lot of the avalanche discussion here is a commonly understood and referenced snowpack profile. It would be a great visual reference to make the discussions and warnings more specific. A few years back we had troublesome storm layer from October which people began referring to as the Halloween layer. I thought that was great because it was memorable and spooky. These discussions with the snowprfile included might also get the discussion focused on not just the old layers when they become a headline but also on when they go away and give people a greater understanding of when they are no longer an issue. I think understanding how much rain or warming or pressure it takes to eliminate a bad layer is also not commonly shared knowledge.

There's a bunch a rambling thoughts for my morning commute. Thanks again for interesting discussion. I am curious how the warning will come together on nwac.
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cumulus
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Re: March 19, 2017, cross post from NWAC obs
« Reply #12 on: 03/22/17, 09:23 AM »

It may exist some where that I am not aware of already but I have felt that a missing piece of a lot of the avalanche discussion here is a commonly understood and referenced snowpack profile. It would be a great visual reference to make the discussions and warnings more specific.

It would be great to have this knowledge! Seems though in reality this would require a nigh near impossible and godlike undertaking.
 
I am trying to imagine a system that would fulfill that... sensors placed in all snowpacks (N-S-E-W) at all elevations all up and down the coast that constantly monitor and send feedback for real time evaluations and postings... Sensors that don't exist and if they did would be fallible and would require placement and servicing, thousands upon thousands of them. Special attention would have to be paid to ridgelines and wind velocity and the snow water content of the snow being pummeled and the winds being channeled off other ridgelines affecting cornice creation and composition and consequent wind slab formation. Crystalline structures and their relationship to snowpack weight would have to be constantly monitored and may quickly change structure in a matter of meters or less, in a matter of hours or less. The tipping point is a precarious one... are you plugged in 24/7? You better be.

Now even if we did have the ability to do that there would remain the matter of cost... and fallibility. It still won't be perfect. Someone will die and the system (organization) will be blamed. Because it was supposed to take responsibility off our hands and it didn't.

The need for foolproof security runs deep in the human psyche... wouldn't it be great? I for one am definitely voting for it the next time it presents itself!
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Stefan
RonL
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Re: March 19, 2017, cross post from NWAC obs
« Reply #13 on: 03/22/17, 09:52 AM »

Ha, sure while I am just daydreaming that sounds great. Let's barcode each flake as it forms and track it in an asset management system throughout the water cycle.

More practically I am thinking a profile drawing by region with the major storm cylces depicted would be a good reference tool to cut and paste in these discussions. We could just continue to develope it as the season progresses and then it shows visually how it evolved throuout the year and could compare years visually in a simple picture.

Just brainstorming ways to better discuss these things in the future... also I am fascinated by the mechanics of big slides like these.
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cumulus
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Re: March 19, 2017, cross post from NWAC obs
« Reply #14 on: 03/22/17, 10:17 AM »


I may have been somewhat Swiftian in my last post, but I do think it's true.

I get what you're saying Ron-- I think a regional snowpack profile schematic would be helpful and provide a good general historical overview and reference, somewhat like the snotels. 
I also think it would be wise to post a big fat disclaimer along with such a profile that it should not be used to forecast avalanche probability. There's way too much variability in terms of aspect, elevation, etc. etc.--as stated above--for a general profile like that to be used accurately as an avalanche predictor.
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Stefan
RonL
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Re: March 19, 2017, cross post from NWAC obs
« Reply #15 on: 03/22/17, 10:41 AM »

I think that is at heart of the reluctance to produce something like this. The experts don't want to risk creditibily with it being wrong or used incorrectly. The avalanche forecasts themselves suffer from that reality and take a lot of criticism.

I just see that a lot is lost with that reluctance get more specific.

My usual questions to myself when something like this happens are along the lines of;

What surface was it on?

What past storm was it related to?

What was I doing back then?

How unusual was that weather event that set this up?

Can I remember the circumstances to identify when this situation sets up similarly in a future season?

Does this mean I shouldn't take that trip I am planning this weekend?

If I don't take the trip this weekend for this reason how long do I wait to feel comfy the danger passed?

If I wait what are the odds my family will not have a shitbarge of expectations for me that weekend and how does their wrath compare to the risk to my life in an avalanche? I kid, sort of...

Not sure my dreamt up profile would answer all that for me but I would pay a higher membership fee to nwac if they answered in email form these questions for me say Friday afternoon each time these discussions make me nervous.
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cumulus
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Re: March 19, 2017, cross post from NWAC obs
« Reply #16 on: 03/22/17, 11:23 AM »

I would pay a higher membership fee to nwac if they answered in email form these questions for me say Friday afternoon

funny!

NWAC relies on you and me and TAY everybody in the community--along with all their more scientific tools and professionals--to issue their reports. Over the years I've seen a lot of cross pollination; info featured on their site that came directly from here and elsewhere. Not sure paying more is gonna offer more closure... but hooray for all you volunteers! Accidental or not. We're all in this together. The snow-pack is an ever-changing beast.
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Stefan
garyabrill
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Re: March 19, 2017, cross post from NWAC obs
« Reply #17 on: 03/22/17, 12:51 PM »

Ron, with deep instabilities be they surface hoar, facets, or bond to ice crusts (or even a wet layer or graupel for awhile), if buried deeply, even recognizing the weak layer and testing it doesn't help all that much unless and until the results become nearly uniform across terrain. For one, even if you get such and such marginal test result, if it is deep, there is no way to evaluate whether or not it could be triggered in any particular location. Just how does your body influence the layer through the overlying snowpack? Could a cornice trigger it? Could a small snow slide trigger it? Exactly how much strength does the overlying snowpack impart to the ability of the snowpack to resist failure? What are the rather nebulous abilities of some particular structure to transmit energy?

And then, too, how does the structure of the snowpack change with location? And what location? What elevation? What aspect? How do the kinds of dynamics in meteorology that Klassen pointed out affect the snowpack here, or there, now or then?

A good place to see the results of a whole bunch of snow profiles is to go to Avalanche.ca, select Glacier National Park, and go to the bottom of the page and choose Snow Profiles. There is a large catalog of profiles. Pick two different ones on or about the same date and see how they vary. Note the 3/17 profile which looks suspect for stability, and then look at the one preceding it in which only a short profile was done because the structure was obviously so good. Choose profiles for the same location on succeeding dates to see how the snowpack at that location changed with time.

Simply, in graphical form the blue represents the hardness of different layers, the little symbols the type of grains, the test results are on the right.
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RonL
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Re: March 19, 2017, cross post from NWAC obs
« Reply #18 on: 03/22/17, 01:30 PM »

I do see how impractical it is, especially the ability to test for instability.

Those profiles are pretty cool though. It took me a minute to orient myself to what they are showing but that is cool to show the locations at different points in time. The change in density seems like it would highlight problems.

It seems like early season readings are changing location with elevation likely because of low snowfall. I was looking at the Macdonald site. I will go thru some more on the coast mtns on the commute home. Thanks
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TN
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Re: March 19, 2017, cross post from NWAC obs
« Reply #19 on: 03/22/17, 06:28 PM »

Thanks for the post, Charlie, I almost missed it.  I was checking hourly today in the Weak Layers section, looking for Ruby Mt something.
I understand the desire of some posters here to see a profile of the snowpack, either at Ruby or anywhere in question.  My approach is to always ASSUME there is a PWL down deep and act accordingly.  Like Karl Klassen wrote, March is not the best time to challenge the mountains, especially not steep slopes below cornices!  Unless you are out there (close to) daily, skiing safe slopes and observing conditions as they occur (like a heli outfit, ski patrol, or VERY avid unemployed ski tourer!), challenging risky slopes is a fools errand (Thanks Gary Brill, I'm not trying to say it better, maybe just echoing)!  Even with that 'pedigree' risk is RISK and March CAN mean few windows of reasonable stability.
It is encouraging that some have posted about their increased caution.  A suggestion would be to get this thread into the Weak Layers section so it doesn't get buried and more folks night see it.  And maybe add the photos from the NWAC report so they are easily accessed for the next few years at least.  I don't see this as only a March 2017 issue but a recurring one, given the exposure of the climbing route, as illustrated in the photos at least.
In this incident at Ruby, I'm particularly interested in the risk to the second party.  I'd love to hear what they have to say, and certainly would LOVE to see a photo of the top from down there.  (Anyone have such?)
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Lowell_Skoog
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Re: March 19, 2017, cross post from NWAC obs
« Reply #20 on: 03/22/17, 09:13 PM »

The upper NE slope of Ruby has a slight, rounded shoulder on the climbers left. You can see it on the topo map. The skiers in the NWAC photo are near (or on) this shoulder.

I think it's fair to say that nobody has ever seen an avalanche of this magnitude on this slope. So it's not unusual for the skin track to wander into the depression where the avalanche ran (though it's better to stay to climbers left), and that's typically where people ski down. Up higher, the up-track tends to be forced back to the climber's right, because it's steeper if you try to go straight up from the shoulder.

The skin track is typically not overhung by cornices. They are farther north, and usually not all that big. This year was apparently much different.

Under typical conditions, I would say that the route followed by the skiers on March 19 is a reasonable way to go. But these were clearly not typical conditions.
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TN
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Re: March 19, 2017, cross post from NWAC obs
« Reply #21 on: 03/22/17, 10:26 PM »

Thanks Lowell!
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"Slow down!  Let ME break trail!  Save the turns and the steep stuff for the way down.  We'll get there sooner,  ski all day and you'll still be able to stand up after dinner tonight!"  The Trail Nazi
vogtski
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Re: March 19, 2017, cross post from NWAC obs
« Reply #22 on: 03/23/17, 06:58 AM »

Thanks to Charlie for posting this, and to all who contributed!

There was also one of these near-Himalayan scale avalanches on the south side of Rainier back in the seventies.  It left a crown fracture at least thirty feet high from Gibraltar across the upper Nisqually, covering most of the glacier with large debris down past the Wilson Crossing almost to the current terminus.
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RonL
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Re: March 19, 2017, cross post from NWAC obs
« Reply #23 on: 03/23/17, 08:22 AM »

I altered my weekend plans partly for weather but also due to the warnings here. I am still a little puzzled by the take away from this discussion. The slides do seem unusual. Is it due to the year being wetter with more sub zero days than normal? Are more of these unusual slides related to the February or November storm layers? Ultimately how long and what am I looking for to feel more comfortable? Is a couple of good freeze thaw cycles in the area I want to ski what I am looking for?

Also, the more I look at those glacier park profiles the more I like them. Mostly it is the thickness of the layer info in the profile that I find interesting. What does it take to produce that? I imagine it is a more rigorous process than me making a hasty pit next to a skin track and poking gloved fingers in the exposed profile. That type of info added to our snotel data seems like it would create a valuable record.

Thanks for any patience you guys have left as I try to translate the info here into my own weekend warrior caveman logic.
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Charlie Hagedorn
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Re: March 19, 2017, cross post from NWAC obs
« Reply #24 on: 03/23/17, 12:51 PM »

Detailed profiles take time, especially for proper documentation.. It gets introduced in a formal way in the (now-changing) level-2 AIARE courses.

The procedures are nicely documented in the SWAG guidelines, viewable in PDF form here: http://www.americanavalancheassociation.org/swag/ Snow profiles start on page 22. Make profiles as clean and square as you can; you know you're getting there when the structure is easily visible.

A great time to practice is a day when the surface snow conditions are poor, or if you have some time on your hands and want to stay engaged/warm-- digging a hole to the center of the earth suddenly seems more interesting.  Though I didn't have the time to fully document, waiting to join up with friends Sunday,  I dug a full [url=http://www.nwac.us/observations/pk/711/]profile/url]. Lotta soggy 1F-or-softer snow in the top 150 cm that day.

Something I'm taking away from this event: while I can't get a good handle on deep instability, I need to more-cautiously allow for the response of any nascent deep instability to a giant trigger. Cornices and warm weather will receive even more respect from me than they already do.

I can't tell you how happy I am that we're having a friendly discussion on TAY instead of mourning as a community. This event could have been very different.

Regarding travel advice, as always: When uncertainty goes up, dial back terrain. Leave a healthy margin of safety.
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