[Ava Blanche]

We talk a lot about digging snow pits, but what should you be looking for in such a pit? A number of sites on the WEB provide direct access to snow profile data, which are a great source for learning more about what we should be looking for when we dig a snow pit.

Producing good snow profiles according to a precise recording standard is one of the most fundamental tasks that any snow avalanche professional does. The Mammoth Ski Patrol has a particularly good site where all sorts of information about avalanches and current conditions is available. One excellent feature of this site is access to their snow profiles, including fracture line profiles recorded after an avalanche has occurred.

Here is the link to one such fracture line profile: http://patrol.mammothmountain.com/snowpits/041209-paranoid1fx.htm

Here is a screen capture of a portion of this profile:



Now just to make sure everyone understands some of the symbology, here is a brief guide (working from left to right across the profile):

1. Shears: where shears occurred. At the bottom of the full profile (see the link) is a description of the type of shear, and other information.

2. Density: not calculated, however, you can get a rough measure of density from the snow hardness index, which is graphically shown by the width of each unit, and is described at the bottom of the graph beside "Hardness". Hardness is described relative to whether a fist (F), 4 fingers (4F), 1 finger (1F), pencil (P), or knife (K) penetrates the snow layer.

3. Form: describes the type of snow crystals present; this is described in more detail at the bottom.

4. Size: average size of snow crystals.

5. H cos 40°: the height of snow above the ground, measured perpindicular to the slope, which in this case is 40°. H is the vertical height. Note that height perpindicular to the ground is what is usually measured.

6. Temperature- in this case, the snow surface temperature was measured as -3°C, which is interesting since the air temperature was +2°C.

Anyway, I think this site provides an excellent starting point to discuss the business of snow pits and snow profiles in more detail. My sincerest congratulations to the Mammoth Ski Patrol for making this information publicly available so that all of us can learn more about avalanche safety.
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There are no easy solutions, only intelligent choices

[Valdez Telehead]

The profiles above are most useful for avalanche professionals collecting data, who have the hour or two to do a full technical profile, identifying all crystal exactly and doing the temp things.

Most recreational skiers don't need to do that, though it is useful if you are visiting the Utah Avy site where they post there pit data in full, to know what things mean.

I think a profile can be done mentally in the field. When you get home just do a sketch of what you found...ie

In this example based on here, we have a couple knife hard layers that are well bridged over weak layers. Also note the slab on slab conditions from two different velocity wind events. Then we have new snow falling, thus masking the visual evidence of wind slabs. These wind slabs are on the surface and not well bonded. Thus this indicates CONSIDERABLE. The offset slabs with some exposed surface indicate spatial variablity.

The "variable settlement" indicates that layers is showing signs of breaking down or fracturing and has lost its bridging strength, but appears to be very slow process.

NOt meant to be really technical, just showing that anyone can draw something useful from their ski day and for future reference.

[Ava Blanche]

I'm not at all suggesting that recreational skiers need to complete formal snow profiles, that is something that only ski area forecasters, highways workers, heli-ski and other commercial recreational operators, and other professionals are expected to do.

However, it is certainly worthwhile for recreational skiers to be able to, first, read a snow profile, which is why, of course, places like Mammoth Ski area and Rogers Pass publish these on their WEB sites. Second, recreational skiers should be looking for the same features in their snow pits that a professional looks for- layering, snow density, temperature, water content, facet and other weak layers, ice crusts, shear planes, etc. The only difference is that a professional needs to formally record their information.

So the main discussion points here were intended to be:

1. How can a snow profile like that above be understood?

2. What specific information from profiles like that above, is useful and should be noted if you are trying to assess avalanche hazard?

I deliberately didn't provide my own analysis of this profile yet; but there is a lot going on that is worth learning about. Also, I am hoping that others will supply additional snow profiles that we can look at and discuss.
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There are no easy solutions, only intelligent choices

[Gary Brill]

I think one of the most important learning points in looking at a profile is to try to understand what combination of variables lead to shear failure and can failure at a some depthe lead to deeper failure.

[Missing Link]

That is quite nice that patrol lets the public access that info.

Question - the form at the shear interface - what symbol is that, I can't find it anywhere - unless its plates (?) but that dosen't seem right plus plates symbol is not darkened in. Also that interesteing looking cloverleaf next to the squares in the basal layer? Not sure what that is either but would like to!

Thanks,

ML

[Mikew]

[Cambria]

First of all, I can get a lot of good info from your observations MikeW so I encourage you keep up the work. The Canadian Avalanche Association has a section on their site called Mountain Trip Talk and I've found I can get a lot of good info from it. My point is even without profile information, we can get a lot of information from other field obs. With my work as a Forecaster, I tend to use profiles as a baseline and then combine that with weather/occurence observations to help back my forecasting decisions. Canadians have a somewhat different recording standard the our US neighbours but there are close similarities. There are a couple of Alaska operations who are posting on the INFOEX who have adopted the CAA standard and it appears to be working well.
A snowprofile is only a piece of the decision making equation.

[DaWiz]

I find the standard snowpro graphs incredibly easy to understand, plus you can note changes in a particular location throughout the season. I agree with MikeW that they are a bit much for the day to day recreational skier, but if you are forecasting for the public or for a particular area they are great. The best part about AvaBlanche's profile (snowpro software) is that it is the accepted industry standard, and any other professional can look at it and understand it. It also allows for data exchange between agencys, such as guiding services or DOT forecasters. The only problem we find with theat system here in the Chugach is that we are rarely able to dig all the way to the ground. Sometimes the data becomes obsolete once significant snowfall puts those layers twelve feet under the surface...
As stated earlier, however, if you were to do a complete data pit and profile every time you went out you would never get any skiing done; but as a forecasting tool and data logging format it works perfectly. The important points are the compression test results and the quality of the shears.
Most of my recreational pits are logged similar to Mike's, but if I have the time I do a full pit and document it in the snowpro software, which graphs it out quite cleanly.
VT, is that depth hoar, or burried surface hoar on your Dec 10 layer, or a layer of facets? Just curious.

[snowdynamics]

VT- That's the most difficult, convaluted profile example I have ever seen.

And not to dog, but Mike- use a ruler for your obs- It's cleaner, and easier to see if that lower resistance layer is fist, four finger or what.

With all due respect to you both, of course.
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www.snowdynamics.com
"Terrain suitable for the conditions."

[Ava Blanche]

Well, first, you can see from some of the posts above why consistency in both what is observed, and how it is presented, is important. This is doubly so when you realize that this is not an exercise where you want to make an error, or have someone misinterpret what is being observed.

Second, many professionals today use a program called Snowpro+ developed by the B.C. Ministry of Transportation and Highways and Gasman Industries of Victoria, B.C. http://www.gasman.com/ to generate their profiles. Snowpro ensures that a consistent high quality product is generated- but remember, the old adage about garbage in equals garbage out still applies; so it is important to ensure that high quality observations are made before they are entered.

Third, it is important to realize that collecting the information above is only a means to an end; it is the data collection portion of the evaluation process. But this process is not complete until the information is used to provide an analysis; to come to a conclusion about what the avalanche hazard is like.

So on that note, perhaps it is time to interpret the profile above. Personally, what I found most intriguing is the presence of the deep ice crust/facet layer in the lower portion of the snowpack, and the thin facet layer resting on bedrock; this does not bode well if it persists and is covered with layer upon layer of new snow. Perhaps someone more familiar with overall conditions in the Mammoth area could comment on how widespread and worrisome this unit is.
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There are no easy solutions, only intelligent choices

[Valdez Telehead]

I was just drawing a PICTUREof the snowpack, not a PROFILE. I said that in my post. Should read it every word. If ava blanche can draw stick-skiers, I can draw a picture of the snowpack.

One correction though...the line with the backslash. it should be double slash to indicate Hard or pencil. I use a single line versus a box with enclosed double slashes,

I use this method to show people with no knowledge and some with knowledge. Many books on avalanches "depict" the snow pack in this manner, mine being a bit more indepth. Nothing odd here folks. I could draw a profile from my pic, or vice versa. Some folks might find it handy to draw what they see.

My full profiles look like yours. I use Hacksaws book. which I already filled up two of them last year (made copies for this year)

Snowpit data is basically to keep track of these things I think. Location including elev. time and aspect of course.....

Grain Type/size
Free Water
Surface deposits
Density
Temp
Snow depth
New snow
Hardness
anymore??

As far as grains, I only use 8 types. I know there are tons more. but the basic 8 types of grains seem good enough. These I have memorized so I don't have to get to obsessed at 0F and wind. trying to get more specific. If I remember something unique about some rounded grains(one of the eight types), I can further investigate and identify it when I get home. I can't belive how many independent grain types there are.

Of course each of these area have subunits.
For instance free water content can be determined in many ways
Its either dry, moist, wet, very wet or slush. This can be done by "FEEL". Even hardness is a "FEEL" test.. while all others are instrument measured.

Wisner..that's the powder that was so sweet that fell after the 10th. Sure you enjoyed it. A subsequent warmer snow event on the 23,24 formed a soft slab over. Actually we had 4.8"WE during that deluge.. That storm was followed by very cold for 36 hours with temps to -10 on the 26th. That soft slab became knife hard very quickly. On the 27th we had 8" of low density...... then the wind blew hard and temps remained moderately cold to 15F or so for the duration of the wind event. That 8" formed the now present wind slabs..Probably the layer Freeze booted with BradA last week. Weather and snowpack profiles work well together.

[Hacksaw]

[Valdez Telehead]

wow,,,,,,sorry. I willl burn them tommorrow..all six sheets(70 cents) of double-sided recycled 8X12 regular paper with 4 "shrunk" copies of your form on each side. Keep them in my desk drawer nice and neat. I transfer my field notes, which is a single laminated work sheet, to my hard files. I have kept the two books I purchased also as special mementos of last years ski record. I have reorganized my pit profile system on your recommendations in the book.

[elk-tamer]

[Hacksaw]