SNOW PITS... good or good for nothing?

Summit - great thread and some good info here. Don't want to reiterate a lot of what is said, I but basically take the same approach as goldenboy: " guess bottom line is that I start with as much info as I possibly can, then try to add to it w/ visual obs, hand pits, pole probing, etc." When digging pits, really trying to just look for new reasons not to go (never a green light to go).

One thing I would add that is not mentioned above, is I actually like to dig a full pit and document the results (more or less) and submit them to the Avy Center that night. Not necessarily a full snow profile, but at least (i) temp gradient, (ii) noticeable layers, (iii) density changes and (iv) some test results.

Reasoning is that it is not for my ski decisions at the time, but just so the Avy Center has one more additional obs to factor into their forecast. The Sierre Avy Center publishes the obs (which is awesome, btw, for really reading up on a ton of info each day), and I feel each additional incremental piece of info adds to a *better* (whatever that means) forecast. Just like individual decisions on a tour, the more info the better IMHO.

Quote:

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Originally Posted by Summit

But the problem is the clues that your slope is "different" are not obvious on the surface. Maybe this valley has a thin mid-storm facet layer or a surface hoar layer that wasn't prevalent in other valleys, or even other slopes in that valley. Sometimes the forecast may even warn "in some areas layer X may be present in a few areas."

Bottom line: Some things you might not find without digging... or having a pucker-factor-moment... or worse. Digging gives early warning.

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Fair enough, for sure. So let's say you dig for layer X and don't find it. Good to go now? Do you dig another? Dig 10? At what point do you have enough info? And even then, what do you do with that info?- It is SO EASY to justify things (CM's delicious "shit sandwich"). Not just asking you, but just in general- I'm not sure if I even know where I stand on it. I guess at that point you go to CM's uncertainty thread..

I dig pretty often, most times not full pits though. I find pits really helpful for indicating the reactive nature of the snow pack at different places in the pack which isn't necessarily observed with visual obs, knowledge of present layers, and overall avalanche forecasted danger.

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Originally Posted by FrontRangeDrummer

I had an experience like this on the same day as the Dry Gultch death. CAIC report looked good, my partner's experience on similar terrain the day before was good, it was a nice day, the run looked really fun, it was sunny, and morale and confidence was high. Then two pits revealed scary things we didn't expect, and we backed off.

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I've had two such scary experiences. In both cases, I had read the CAIC report, I had skied a similar slope angle on the same aspect in the same/adjacent drainage the previous day, and I had dug into the snow to investigate the layering both days. There were no significant changes in weather overnight. Everything, right up to the stability testing, indicated that these slopes were equivalent. This turned into a classic case of finding a reason not to ski.

In hindsight, I wasn't able to make many observations on either approach. One was early fall with little snow anywhere else, the other time we approached up the opposite aspect on a gentle ridge. The pit may have been unnecessary if I had test slopes and other things to asses both the layering and stability.

It never ceases to amaze me how complex and integrative stability decisions are.

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Originally Posted by spthomson

And I pole probe, too, but what does that really tell us?

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When we probe we are trying to surmise what layers exist by guessing from the varying resistance we feel = fancy way to say IT IS A GUESS. Probing can tell you a lot of indirect information and it can miss a lot of things. I think it is super useful as long as long as you remember the limitations.

EXAMPLE:

Today I went out to work with someone on their pits. I probed in an area I hadn't been to in a bit on an aspect I normally don't ski (SE). We both probed and said "I feel new storm snow underlain by a barely perceptible crust, then harder snow (slab,) and soft at the bottom, certainly facets."

I knew to look for that upper crust because I knew it was there before the storm. But in my pit, I found two more decomposing crusts in the lower 1/3 of the pack with near crust facets. I knew one was there because I'd seen it in the past, but I didn't feel it probing. The other I didn't expect.

THOUGHTS ON APPLICATION AND LIMITATION:

I use both my collapsible probe and my poles because if I really want a sensitive feel, I need to vary the surface area just like poking the walls of a snow pit.

Approximate hand hardness scale equivalents:
Probe ~ 1F to P
Pole Handle ~ 2F to 4F
Pole Basket ~ F to F+ depending on the basket size

Remember that you are compressing the above layers into the lower layers which will decrease your sensation. One way to overcome this and detect thin crusts is to plunge your basket down and then when withdrawing, scrape along the sides.

As Cookiemonster mentioned, the research shows probing is NOT going to find all the layers, particularly the thin weak layer, for example, the nefarious persistent layer that kills: buried surface hoar.

Here is a great idea one of my mentors showed me: if you dig a pit, particularly a deeper one, the last thing you do before filling it in should be to probe so you can directly correlate what you feel to what you see. This theoretically gives you a better sense of what to feel for and look for change in.

In response to acinpdx here are some useful ways to collect information really quickly:

- hasty pits or hand pits (described in thread)

- pole probing. But it has limits - described in thread. I try to get around that a bit by reversing the pole and stabbing the handle into the snow rather then the basket. Still a pretty gross/rough test and only shows top layers

- On a kickturn sometimes I'll skin above the old kickturn and cut a new track that then descends to the old track. Very rough test to show surface slab

- on the skintrack skin over to convexities/small pillows and ski cut them. This is very common also. I look to bomb pillows on top of other pillows because its fun but also because its good information.

- if you're close to a pillow scrape off some snow real quick to show you the layering. A nice convenient pillow that has a flat side is basically an already dug pit - albeit one that's been exposed to air or wind.

- I like to break new trail every now and then. Ski penetration can tell you a lot. When doing so if there's a convenient rocky spot or treed or krumholz spot I'll do a quick pole or hand excavation to look for facets.

That's all i can think of right now. I'm sure I'll think of others i've forgotten or others will chime in with some other useful little things they do.

and yeah, I do snow pits usually when I have little knowledge of the snow pack.




the common thread on all this is that I use this to look for signs of instability not to look for signs of stability.

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Originally Posted by Hugh Conway

digging enough pits isn't particularly practical in touring some terrain; other observations of the snowpack can be.

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Indeed! This problem is no rarity! In such situations, you have to rely on your brain, eyes, experience/education, forecast, and data from similar slopes. When you can't test the slope in question or find a representative slope to test, it increases uncertainty. Uncertainty should encourage conservative decision making with special thought given to the exposure (consequence).

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Originally Posted by CookieMonster

Just for clarification: I wasn't writing in reference to your post, nor the concepts and methods outlined therein ... which were excellent ( as I noted ).

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Indeed, I was unclear. I quoted you because what you said backed my point. The rest of the response was in response to Goldenboy, not to the quote of you I used in support. I added a clarification to the post.

Quote:

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Originally Posted by CookieMonster

if this thread were the appropriate place, I would write about the dangers of excessive conservatism.

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I think that could be a very interesting thread. You should start it!

good read, thanks. When I was fresh from my avy course I did pits lots. It seemed like that was one of the main things to do, but I found them hard to/didn't know how to apply to big picture. Now I don't do them very often and it's more to see how what has been going on looks in the snow and also as a visual reminder, oh yeah there's that layer from x.

I like doing them, just with a different perspective now.

I like to dig pits to check that the place I'm in agrees with the forecast. If the pit didn't agree with the forecast, then the reason needs to be explored. (pit in a wierd place or forcast not applicable).

In terms of using a pit for go/no-go: I've never really been able to get much out of the different tests.

thanks for starting the thread.

i don't always dig pits, especially full pits, but feel like i've made some live preserving decisions based on pit results. i feel like i've made good go/no-go decisions based on gathering other types of information many times.

Lots of great discussion here. I like a few things mentioned below by LeeLau. There are few things more educational to me than purposely causing short sloughs, slab releases, or propagation whether it is stepping off the skin track or ski cutting over steep sheltered terrain. "Sportvalanching" in short stepped areas is a fun and relatively safe method of examining not only snowpack, but how it feels to ski in/escape moving snow (note this is done with skins off of course).

Quote:

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Originally Posted by LeeLau

- On a kickturn sometimes I'll skin above the old kickturn and cut a new track that then descends to the old track. Very rough test to show surface slab

- on the skintrack skin over to convexities/small pillows and ski cut them. This is very common also. I look to bomb pillows on top of other pillows because its fun but also because its good information.

- if you're close to a pillow scrape off some snow real quick to show you the layering. A nice convenient pillow that has a flat side is basically an already dug pit - albeit one that's been exposed to air or wind.

- I like to break new trail every now and then. Ski penetration can tell you a lot. When doing so if there's a convenient rocky spot or treed or krumholz spot I'll do a quick pole or hand excavation to look for facets.

the common thread on all this is that I use this to look for signs of instability not to look for signs of stability.

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Summit's comments on pole probing are particularly interesting. I certainly poke around a bunch with my poles, but these steps add quite a bit of articulation to the observations along the way.

Quote:

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Originally Posted by Summit

THOUGHTS ON APPLICATION AND LIMITATION:

I use both my collapsible probe and my poles because if I really want a sensitive feel, I need to vary the surface area just like poking the walls of a snow pit.

Approximate hand hardness scale equivalents:
Probe ~ 1F to P
Pole Handle ~ 2F to 4F
Pole Basket ~ F to F+ depending on the basket size

Remember that you are compressing the above layers into the lower layers which will decrease your sensation. One way to overcome this and detect thin crusts is to plunge your basket down and then when withdrawing, scrape along the sides.

As Cookiemonster mentioned, the research shows probing is NOT going to find all the layers, particularly the thin weak layer, for example, the nefarious persistent layer that kills: buried surface hoar.

Here is a great idea one of my mentors showed me: if you dig a pit, particularly a deeper one, the last thing you do before filling it in should be to probe so you can directly correlate what you feel to what you see. This theoretically gives you a better sense of what to feel for and look for change in.

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I feel fairly comfortable with how I've made choices in the past but I'm now struggling with the middle ground. With higher danger/less experienced groups the choice is fairly safe terrain. High consequence lines are typically skied during low danger with high confidence in the snowpack. Getting to that level of experience/comfort level where bigger faces/lines could be skied with fresh snow would be a good next step. I see it all the time in this area, but how one gets to a point where they can ski Wang Chung Face on Axtel (steep cliffed out open face) with 12"+ inches of fairly new snow, is sort of a mystery at this point. More pits on a regular basis could obviously assist in this pursuit,but there's just no substitute for knowing conditions by being out in them all the time in similar terrain over any given season.

Great Thread.

Because of the rapidly changing conditions in the PNW, I will usually dig a pit and do a shovel shear or compression test if other observations indicate stability. That said, I generally pass on the pit/test if general avi danger is low and there are fresh tracks where I'm about to ski.

Question for the collective - when you dig a pit, how many of you record your profile & failure results, and send to your local avi center? I know that NW Avalanche Center likes field observations - what about CAIC, UAC, etc? I send in sometimes, but the effort to record/transcribe into NWAC's form makes it a hit/miss exercise.

Leelau hit the nail on the head. This is wot I do on the uptrack as there is nothing better than having my ski (split board) on the snow and play with features and pillows. (yes I haave fallen off said pillow as it collapsed)
The main thought running thru my head while reading all this is that we are telling newbies and lurkers not to dig pits (sorta kinda).
I encourage people I tour with to dig and probe regularly because just like our beacons, how many people practise with these things that may one day save MY life! then I think about YOUR first aid kit etc etc. many slackcountry packs are empty other than shovel/probe, well, other than water,lip balm and granola bars.
Digging a pit is snow study, and how can that be a bad thing? When I return to Canada each season I dig several pits, usually 2 per day, with full snow study obb"s so my brain is back on the game and I'm familure with all items in my pack. Even when people skin past me to drop big lines. Forget last year, or even your last trip, shit changes and just like we remember how good that slackcountry line skied late season only to find its an alder field, we feel the same about our gear, complacency. use it or lose it mind set.
So many people just want to get to the safety meeting. One time huckin eh? set up a avy scenario for our group and they all blew it off for the safety meeting and to chat, leaving me to practise on the scenario by myself.
Lets face it, we all could do with more tranny training, and I feel the same about the rest of the gear. Who here has dug in avy debrie, just because? a cave, just because?
I don't want to sound holyer than thou, but I told one guy to get out his probe and take a depth measurement( while he stood around as I dug a pit) and he said he didn't want to coz he would have to dry it out tonite. Huckin eh? and I dug a pit one time, and the boys had safety meeting and after about 10mins a guy came over and asked wot did you find ... ??? SNOW!!!
Most of us here have toured solo, and I do regularly, coz so many of these people are not able to make appropriate decisions as they haven't checked the CAA bulliten etc etc, and I find, me (the drunken ozy snowboarder) making decissions for the group and having to repeatedly explain why. Solo I don't have to justify mellow terrain choises and stopping for a "good-old-hole-digging!"
Rant over, no I'm not drunk.

bumpin a good thread.
Overall here in Wasangles I dig a lot of pits early to see what's goin on.
Some se4asons I,m pretty much done carryin a pit kit come feb.
Unless there are weird shizz like an mlk raincrust above 10k
I'm lookin for or out on a data mission
season fore last was interestin till late march
pullin low teen ct's on six' slabs was spooky to say the least
http://i5.photobucket.com/albums/y19...esfeb10185.jpg
as was stuff like this pit attempt
http://i5.photobucket.com/albums/y19...esfeb10011.jpg

don't spend time digging pits out here. tons of variability. the weather, wind/moisture play a big role in limiting any lingering instabilities.

pole probing, hasty handers, and spending multiple days a week up high works for me.

since most of our above treeline terrain is steep/wicked steep, ski cuts are paramount.

never really looking for reasons not to ski something, always looking for ways to roam about and ski things as safely as i can. if i can. always something to ski when conditions are scary.

rog

Field observations vs snowpack tests: Which is best when?

Ahh, yes, I remember this thread....an excellent thread and a great time of year to bring it back, as everybody is slowly gearing back up and getting ready to head back out into their various gnar.

This thread has the goods, if you look through the various posts...analytical snow pit datasets vs. slightly more casual probing, and general terrain and depth observations.

I think it depends how a person's head is set-up. In the laboratory, I'm very analytical...and know that aggregate minor mistakes just widens one's margin of error, so I do everything I can to absolutely minimize every error potential. But in the mountains, there are so many factors that you can't analyze every single one...so it becomes a factor of intuition combined with experience.

Some people are analytical and will always want to be digging pits to back up their observations out there....others will hardly dig a snow pit, even if they have the time and will go on their gut and some pole-probing. Is one better than the other? No...just different tactics to match different personalities. I'm sort of in the middle but tend more towards gut instinct and probing.

The KEY is whatever tack you take, NEVER rely on a single dataset....just like you wouldn't base all your movements on a few pole-probings in a specific area. Just like has been hammered in this thread and this forum, there are WAY too many variables in snowpack density...can be different 2 meters away, for a single test pit to give substantial OVER-RIDING validity. If it makes you feel better/safer to spend all day digging multiple pits in a grid pattern...then sure, your data will be more valid...but do you need to? Depends on the person.

Dig your snow pit or don't dig your pit...just make sure, whatever you do that you're comfortable with your decision. Your gut starts to tweak on you? Then you know you have to look around and re-evaluate.

Be safe out there, that's for sure. Just know that no matter how many different tests you use, the mountains tend to play by their own game...you're not the referee. Just a player. Knowing that you CAN get squashed by a big 350 lb linebacker if you don't stay on your toes and move lively...that's the pulse-quickening aspect of why we go out there, otherwise we'd all be staying home and watching the game on tv, me thinks.

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Quote:

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Originally Posted by Alaskan Rover

Ahh, yes, I remember this thread....an excellent thread and a great time of year to bring it back, as everybody is slowly gearing back up and getting ready to head back out into their various gnar.

This thread has the goods, if you look through the various posts...analytical snow pit datasets vs. slightly more casual probing, and general terrain and depth observations.

I think it depends how a person's head is set-up. In the laboratory, I'm very analytical...and know that aggregate minor mistakes just widens one's margin of error, so I do everything I can to absolutely minimize every error potential. But in the mountains, there are so many factors that you can't analyze every single one...so it becomes a factor of intuition combined with experience.

Some people are analytical and will always want to be digging pits to back up their observations out there....others will hardly dig a snow pit, even if they have the time and will go on their gut and some pole-probing. Is one better than the other? No...just different tactics to match different personalities. I'm sort of in the middle but tend more towards gut instinct and probing.

The KEY is whatever tack you take, NEVER rely on a single dataset....just like you wouldn't base all your movements on a few pole-probings in a specific area. Just like has been hammered in this thread and this forum, there are WAY too many variables in snowpack density...can be different 2 meters away, for a single test pit to give substantial OVER-RIDING validity. If it makes you feel better/safer to spend all day digging multiple pits in a grid pattern...then sure, your data will be more valid...but do you need to? Depends on the person.

Dig your snow pit or don't dig your pit...just make sure, whatever you do that you're comfortable with your decision. Your gut starts to tweak on you? Then you know you have to look around and re-evaluate.

Be safe out there, that's for sure. Just know that no matter how many different tests you use, the mountains tend to play by their own game...you're not the referee. Just a player. Knowing that you CAN get squashed by a big 350 lb linebacker if you don't stay on your toes and move lively...that's the pulse-quickening aspect of why we go out there, otherwise we'd all be staying home and watching the game on tv, me thinks.

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strong post I doubt the great thread tag will ever be bestowed on the crap you start :rolleyes2but well we all start the threads we want
scariest pit I ever dug
http://i5.photobucket.com/albums/y19...hbum/sf002.jpg
high danger day
collapsed as a partner dropped into pit to help
sympathetically released whole skiers right slope
knew shit was diceey that day but a few sucessful ski cuts and some sking of bed surfaces led to a great day of learning and a safe return to the trailhead witgh my crew
one of my partners asks
"what will you need to find in that pit to decide whether to ski that slope"
a lot
good question IMO

Fuck that was informative!!! Took me about an hour from start to finish but was cool to see opinions. If I am skiing my back yard I dont think I have ever dug a pit but just from observations and guys that have been rocking the same mountain for years. The mountain tells you what slides when, how often, under which loads. On heavy snow fall days we have average to steep lines that are very protected sub alpine that in the last 30 years no one has ever seen slide. But 30m west on a slightly different aspect its a totally different story.

If I see the winter develop season long I know whats there. If not ill dig but I cant say I do more than 4 a season. Its easy to get caught up in pit results. Identifying all the other signs is a much how to say "be totally aware of your surroundings". Get all nature boy and be part of the environment. Sounds hippy as shit but its the truth.

other side shot
glad the pit wasn't dug there
http://i5.photobucket.com/albums/y19...m/P1011327.jpg
Sometimes ya know what you're lookin for but the act of findin it is important
http://i5.photobucket.com/albums/y19...ski/tlp004.jpg
who wants to be dope on a rope lookin for shit in the pit today:wink:
http://i5.photobucket.com/albums/y19...ki/toph052.jpg

nice pics Dibbs- I dug very few pits last season, but most of the days I was bc were usually days after a storm since I ride lifts on pow days, and from paying attention to pole probing and skinning up/kicking some smaller cornices and stomping in the snow at switchbacks my group never really felt the urgency of digging a pit. we also didn't ski TOO much seriously dangerous terrain. It's neat seeing pics from high danger days and how that affected the pits you dug.

From Ed LaChapelle (1980)

Formally stated, the steps in avalanche forecasting are these:

1) Available data is collected about the place and time in question. Some of the data may be vague, (second hand reports, past weather trends), while others may be quite precise (snowfall records, avalanche records, weather maps).

2) A hypothesis about snow stability is formed on the basis of the initially available data. (A first estimate may see an unstable snow pattern, or the amount of snow required to overload a slope may be anticipated.)

3) The hypothesis is tested through observation and experiment. (Field checks are made for avalanche occurrence, mechanical tests are made for failure planes in new snow, or artificial release is attempted.)

4) On the basis of tests, the hypothesis is confirmed or revised. This test revision process may be repeated a number of times over time spans ranging anywhere from hours to months, if a sufficiently reliable picture about snow stability has not yet emerged.

5) Finally, the hypothesis is revised or confirmed to the point that it is seen to represent current reality of the snow cover. An evaluation or prediction is made. (Safe slopes are are selected for skiing, a degree of hazard is estimated, or on avalanche warning is issued.)

6) Actual avalanche occurrences (or non-occurrences) are monitored to check prediction accuracy.

The essence is always to have in hand an opinion, no matter how vague or ill-informed at first, about the current state of snow stability. The opinion can be revised and improved as more clues become available. The error is to have had no opinion at all, to have started building no prior knowledge, before a decision has to be made

A fairly concise description of an incredibly complicated process. Snow pits? Definitely good for something but just one small piece of puzzle.

Here's how I look at digging and stability tests.

Day tours in areas where I'm familiar with the snowpack: I'll read the public bulletin and probably won't dig. I'll rely on field observations and poke around in the upper snowpack using a pole test or hand shear. If there's something ugly in the public bulletin I may investigate further.

Day tours in areas where I'm not familiar with the snowpack: Same as above but if the bulletin is reporting tricky conditions I'll dig once or twice to see what's going on.

Trips where I'll be in the area for more than a couple of days and familiar with the snowpack: Depends what's going on. If there's something to watch for or a significant change during the trip I'll dig to evaluate what's going on. If things are generally stable with little change I'll rely on field observations for the most part.

Trips where I'll be in the area for more than a couple of days and not familiar with the snowpack: I'll probably dig a decent profile at the beginning of the trip to get a baseline on what the snowpack looks like. For the first couple of days I'll dig several more times in various locations to get an idea of consistency in relation to what I saw in the original profile. After that I'll be comfortable with my read on the snowpack and will monitor any tricky layers or reevaluate if there's significant change.

Where digging really has it's place is when you're dealing with a persistent weak layer (PWL). It's handy to confirm distribution and consistency of the PWL:

If you dig a bunch of holes and the PWL shows up in all of them and produces similar results you know what you're dealing with is widespread and you need to choose terrain accordingly.

If you dig a bunch of holes and the PWL only shows up in specific areas (ie, a certain aspect and elevation) you can start to isolate the problem to those specific areas. This requires due diligence and keen observation skills in your investigation because you need to be sure you've been thorough in isolating the PWL to those specific areas. There's serious potential for dire consequences if you fuck this one up.

If you dig a bunch of holes and the PWL shows up randomly here and there with no consistency in it's distribution and/or test results you have a sketchy situation on your hands. You can stress out about what areas are safe and what aren't or you can just treat it like it's a widespread problem and choose terrain accordingly.

Quote:

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Originally Posted by skifishbum

strong post I doubt the great thread tag will ever be bestowed on the crap you start :rolleyes2but well we all start the threads we want
scariest pit I ever dug
http://i5.photobucket.com/albums/y19...hbum/sf002.jpg
high danger day
collapsed as a partner dropped into pit to help
sympathetically released whole skiers right slope
knew shit was diceey that day but a few sucessful ski cuts and some sking of bed surfaces led to a great day of learning and a safe return to the trailhead witgh my crew
one of my partners asks
"what will you need to find in that pit to decide whether to ski that slope"
a lot
good question IMO

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Nice pix. I take it you concluded the pit test pretty 'rapidly' after THAT. But at least there was a tree close by at the initiation point, if that slab had decided to go for a nice trip. Trees have saved my ass more than once!!

Johnny Casino:
Thanks for the good vid of the professor discussing snowpack analysis. Some good points in there, for sure. That codger reminds so much of this professor at the Geophysical Institute in Fairbanks....actually he reminds me of about 15 people there!

But will someone PLEASE break the telescoping antenna off of their car and give it to this guy, so he can use the damn thing as a POINTER. Sometimes professors forget that they are NOT invisible.




Hey, Professor...get one of these: They work great!!! (as a lecture pointer, not a snow probe ;) )

http://buy.traxxas.com/images/products/2017.jpg

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ah ha!!!

http://i5.photobucket.com/albums/y19...ki/toph052.jpg

now i remember you. my only memory is passing you while heading out to the g line. you had a few folks with you, i was solo. thanx for breaking trail part way out! you didn't seem very amused at my passing your group. oh well:)

twas a great run if i remeber correctly.

rog

Seems like weather observations, local slide activity, and local propensity for activity are pretty important.
I've usually decided to ski something before I dig. I go to UT from CO and the snow seems much more cohesive. Then go to the the pacific northwest maritime snow takes that up an exponent. Familiarity breeds contempt but maintaining a healthy respect will see you thru to another day.