What an awesome discussion everyone! I finally found this discussion after a PM from J.Spin on ESUWX Forums but I will chime in with some thoughts now that I've read through the thread.
First off, great information from Tony regarding the densities from the various climates. I'll get to my thoughts on snow densities later on... there are a lot of topics covered in this thread and I'd like to touch on them all.
Ski Resort Marketing and Snowfall Totals
As many know (but many also don't know) I am employed by the Mount Mansfield Company (Stowe Mtn Resort) and work in the Marketing Department as one of the two winter-time Snow Reporters. One of the fun things about being a snow reporter is that while you are technically a marketing employee, you are based out of Mountain Operations which is filled with fun but no-nonsense people who are only concerned with the day-to-day operations of the resort. Wind, temperatures, snowfall, precipitation, it is all very important to be as close to spot-on as possible with this information when dealing with mountain operations because it actually has an impact on the work that needs to be done that day (ie. how extensive do we need to groom, are snowmaking needs temporarily alleviated on some trails, etc). There is no "marketing" tweaks done to this information and the same information disseminated to Mtn Ops is posted on the Stowe website. Now, snowfall measurements on a mountain that is several miles wide with elevations ranging from 1,300ft-3,700ft is not an exact science but we are trying hard to get it as close to accurate as possible. The snowfall differences around the mountain can be striking at times and it should be noted that our measurements are done on Mansfield and not Spruce Peak which I have seen can get significantly less snow than Mansfield.
I have been skiing at Stowe, and on Mansfield, since the fall of 2003 (so I still only have 7 years of weather/snowfall experience on the hill). I bought my first seasons pass there when I moved up to Burlington to go to college at UVM...and I purchased my pass before ever skiing there; I was just told that Mansfield was the mountain to ski by some knowledgeable UVM grads. Needless to say, after my first season there I was hooked as Mansfield is unlike any other mountain in the northeast in terms of terrain/snowfall combo. I do like Jay Peak a lot, but IMHO it is not Mansfield. I am not talking about the respective resorts on these mountains, but the mountains themselves. The size and scope of the skiable terrain on Mansfield stretches over miles and can land you in 4 different towns. I also think the history of skiing on Mansfield (first ever ski patrol, CCC trails, etc) is unmatched in the east and its long history is also why there are great ski trails (backcountry and inbounds) all over the mountain. My love of the mountain is eventually what brought me in touch with Stowe Mtn Resort marketing... basically through years of posting pictures, weather forecasts, and trip reports from Mansfield all over the internet. I tell you this because although I work for the marketing department in the winter, I am a skier and weather/science guy first.
Now, I've heard some comments that ski area marketers like to inflate snowfall totals...though oddly this is only really inferred when talking about East Coast resorts (I'm not sure I've ever heard anyone question a Western mountain's snowfall). People think that ski area marketing is the reason for the discrepancy between the stake's 230" total and the resort's 330" average total (which should actually fall thanks to last season's paltry 246" total; however 31.5" was recorded at the stake after we closed which is not included in our operating season total). Stowe's listed snowfall is a 10-year average and anyone that has been paying attention knows that the 2000-2010 was overall quite favorable with over 300" most seasons, including a couple 400 inchers (2001 was over 400" and 2007 ended up right near 400"). 2008 and 2009 saw 330-350" and 2010 was 246" (by far the lowest snowfall total since I started skiing Stowe in 2003). The seasonal snowfall total is the summit snowfall total (base area is probably as much as 100" less being a full 2,000 vertical feet lower).
As far as marketing interfering with snowfall totals... that is flat out wrong. In my 2 years of being a snow reporter there has NEVER been any pressure from upper management to report more snow. Not even a hint of it. Our snowfall totals are generated by me and my colleague personally measuring snow around the mountain and that data is supplemented by members of the ski patrol and grooming departments (grooming helps largely with the 6am upper mountain readings; I personally measure only base area snowfall for the 6am report but then measure all over the mountain throughout the ski day to get an idea of accumulations). Also, members of the ski patrol have been trained by the scientists at the Mount Washington Observatory in how to measure snow in harsh, windy climates. From this training, ski patrol has set up snow study plots at various elevations, much like resorts out west, and we keep detailed daily logs in an excel spreadsheet of weather conditions and snowfall. There are two main plots that include a fixed snow stake for measuring snowpack (listed as our natural snow base depths on the stowe.com/report conditions page) and a plywood board for measuring new snow. One plot is near 3,000ft in the woods near the High Road/Perry Merrill intersection off of the Gondola. Another is down at near 1,600ft behind Barnes Camp (old building next to the parking area at the winter-time road closure of RT108) just off the Snowcat work road that goes between Spruce Peak and Mansfield.
I used to think that resorts inflated snowfall totals before moving up to northern Vermont and working at Stowe. This is obviously talked about greatly in the ski industry and there is a general assumption that the less average snowfall a mountain receives and the closer it is to a large population center, the more incentive there is for them to inflate their totals so skiers do not pass by those areas to go further north to the historically more snowy spots. Anyone that frequents places like Jay Peak, Smuggs, Stowe, Bolton, MRG, or Sugarbush knows that these places do actually get a lot of snow. Snowfall averages at these areas are on par with many inter-mountain west resorts. Everyday I compare our snowfall with Smuggs' snowfall (Stowe's neighbor on the other side of the Notch) and its generally about the same. In 2008-2009, Smuggs recorded 353" while at Stowe we recorded 349"... which I found pretty remarkable that independent parties measured nearly identical amounts of snow between the two resorts that are only a 1-2 miles apart. As J.Spin has mentioned, I really doubt there is a collaborative effort between resorts to mislead the public with regards to snowfall totals...and it is probably not by chance that snowfall averages decrease in a very organized fashion from Jay Peak south to Killington.
Lastly, there is a social element to snow reporting... the Stowe locals would crucify me if I inflated the totals. I know a ton of the local crowd that frequents that mountain and they know who is measuring, so my name is on the line. I can most certainly see how people think/assume ski areas inflate totals, but I would almost say that a lot of times we are actually quite conservative with the amount of snowfall on the hill. I got called out more than a couple of times last season for under-reporting snowfall. Even if I suspect the actual amounts might be higher than my measuring spots are showing for whatever reason, I will always go with what I actually measure.
http://list.uvm.edu/cgi-bin/wa?A2=i...4CA9396E52&Y=braaten.scott@GMAIL.COM&P=119929
then
http://list.uvm.edu/cgi-bin/wa?A2=i...4CA9396E52&Y=braaten.scott@GMAIL.COM&P=125875
Mansfield Stake Data
Ahh, the stake. So much lore and yet it begs so many questions. The stake is only useful in my mind for a comparison of snow depth from year to year and not actual snowfall (though I may be biased because I do believe the northern VT mountains, Bolton to Jay, do receive 300" per year on average). Sometimes the stake measurement is spot on, especially if a storm is just winding down or it was snowing during the daytime. A wind-less storm is usually well reported but wind rarely stops at 4,000ft in the low level jet. Other times the amount of "NEW" snow reported is just flat out wrong and not even close to what actually happened on the hill. In Mountain Operations, we frequently get a kick out of how low the "NEW" snowfall reported is when compared with what we have actually seen on the mountain. Even the groomers joke about how they just groomed the deepest "trace" anyone's ever seen. I believe local topography, wind, and collection method has a lot to do with this.
If Tony is right and they use a cylinder to measure snow up there, it would explain a lot because in high winds a bucket is going to under-catch significantly. This would make sense because sometimes you will see the actual snow depth increase MORE than what they report in the new snow column. Wind is the major factor up there and this is likely the large reason for the snowfall discrepancy between the Stake and what actually falls on Mansfield. In fact, wind might result in less total snowfall measured day-to-day because wind effects density and loft... more on this later.
Another large part of the discrepancy in snowfall is the practice of one measurement per day at a fixed time. At the very least, you should measure snowfall right when the snow actually stops falling but NWS guidelines allow for up to 4 cleared measurements per day (1 every 6 hours). When measuring at the stake, I've noticed that since they only report once a day at 4pm, they do not report snowfall if it fell and melted within that 24 hour period. If 4" falls and then is washed away by rain, you still record the 4" as snowfall. Oftentimes in marginal temperature profiles, nighttime is when you are going to be able to accumulate snow before precipitation goes back to rain during the daytime. I can remember two storms this winter when it snowed several inches of wet heavy snow overnight on the front-end of the system, before turning to rain during the daytime as warm air surged northward. One storm we had 5" at the summit at 6am which was washed away during the course of the day and the stake showed it as 1.5". The other storm we recorded 4" and the stake showed a trace at 4pm. I would also wonder about just how diligent the engineers are about getting a good snowfall measurement. If it has been snowing hard for a day straight but with high winds, I wonder just how much effort they put in to get a good measurement or if they just check the bucket and record that without thinking about it (such as the 24" on Valentines Day 2007 which seemed like a very low estimation in my mind).
The stake does have one awesome redeeming value and that is comparing snow depths between winters. However, I have found that there isn't always a direct relationship between snow depth and the amount of actual snowfall that has fallen. For example, we have gotten spoiled the past 5 winters (basically the past 10 winters, too) with largely above normal maximum snow depths as you can see in the graph below. 2005-2006 was the worst in terms of snow depth as seen by the red line.
Last season was the most odd though, as we reached 100" of settled depth about a month earlier than the historical max, even though the ski area only had recorded 200" of seasonal snowfall. That is a 2:1 snowfall to depth ratio. I like to compare snowfall to depth because it gives an idea on the amount of settling and thus the type of snow falling (works best out west where snow that falls doesn't melt or thaw out). Usually, at Stowe we have closer to a 3:1 total snowfall to depth ratio (likely higher than it should be due to rain/ice events). The reason that Mansfield hit 100" of depth with only 200" of snowfall this season was primarily because of a few big Sierra Cement storms, coupled with no real big thaws. Mid to late February we particularly got hit hard with massive dense snowfalls that totaled near 4 feet at the summit with 3-5" of liquid falling on the mountain. That storm was primarily needle flakes (flake type effects density greatly) and a moist needle at that with an isothermal column just a touch below freezing.
Snowfall Densities
I have noticed in casual observation that intermountain west ski areas usually have a 3:1 or even higher snowfall to depth ratio. I bet you any Utah or Colorado or Wyoming resort that gets to 100" of settled base has received 300"+ of snowfall to get there while the coastal mountains out west are probably closer to a 2:1 snowfall to depth ratio (ie. Kirkwood with 500" of snowfall and a 250" base, while Alta sees 500" and only has 140" on the ground). Tony's analysis makes sense to me in that our East Coast average snowfall density isn't as low as the inter-mountain west, but it also isn't as heavy as the coastal ranges.
I do think the average density of snowfall varies greatly among East Coast resorts as resorts that rely on purely synoptic snowstorms (like a nor'easter), such as the Berkshires, Poconos, Catskills (though some Lake Effect reaches them) and portions of the Whites, will often end up with a near 10% snow density. While synoptic snowfall does vary in density, it is documented that snowfall ratios in nor'easters on the east coast averages near 10-12:1 regardless of elevation. A lot of that is a function of flake type and wind (nor'easters often come with a lot of wind).
Wind is a huge factor in snowfall measurements, as well as densities, and this is often vastly over-looked. First off, think of what a good low-water content snow is made up of? Mostly air with a little bit of substance, as the big spindly arms of a dendrite crystal cause them to stack on top of each other, trapping air in the snowpack, like potato chips do in a bag. In a way, the density is basically a measure of how efficient the snowflakes are at accumulating. Wind can drastically alter snow accumulation efficiency and I'm betting that the majority of low density snowfalls occur with relatively little wind and that those flakes were formed at a very favorable snow-growth temperature (more on flake types and temperatures below).
What would be a very fluffy snowfall with 4% water-content in a calm environment can turn into a 10% water-content snowfall in a windy environment because flakes become wind-packed together with no loft. Good dendrites that would produce high ratio snowfall become fragmented and shatter from collision in a windy environment, thus losing their loft-building characteristics. This brings me back to the Mansfield Stake and the local topography on Mansfield... most of our upslope snowfall (generally a fluffy snow in mid-winter) comes from a strong NW wind flow lifting moisture over the 4,000ft ridge. Stowe Mountain Resort occupies the eastern side of the mountain, which in some respects is sheltered from the wind (while Stowe is a windy ski area, it still pales in comparison to the wind experienced up on the ridge of Mansfield). It is no surprise that the deepest snow on the mountain is found in the wind-sheltered areas because those flakes are able to build loft and thus accumulate to a deeper depth. I often find that our deepest snowfall measurements are not at the very top of the mountain, but down closer to 3,000-3,300ft in elevation and out of the wind (ie. the Rim Rock, Cliff Trail, Bypass, ND Glades region). In some situations, I've even seen calm conditions near the base area at 1,500ft allow for a greater snowfall measurement than up above 3,500ft, even though more precipitation has likely fallen at the summit...the snow has just been packed-out by the wind up there.
As I alluded to earlier, flake type is also a primary factor in snowfall densities and this has more of an effect on density than even surface temperatures in most cases. With good dendrites, you can still get a relatively fluffy snowfall at temperatures near 32F...however, it can be 5F outside and if you are seeing needles as the snowflake type, you can rest assured the density will not be much better than 10%. Needles produce absolutely no loft and thus trap no air in the snow; if dendrites are like potato chips, then needles are like grains of rice.
In order to get the best loft building dendrites, you want the maximum upward motion (lift) in the atmosphere to occur at temperatures between -12C and -18C (roughly 0F to +10F). This is what meteorologists refer to as the best snow-growth zone. After dendrites, plates are the next favorable flake type, while anything resembling a needle is significantly less efficient at accumulating. Given a wind-less environment, you can expect 20-40:1 ratios from pure dendrites and that falls to <10:1 ratios in small needles. Here's a chart that shows what flake type you can expect to form given the temperature of the atmosphere in the area of strongest lift.
I have sort of written off surface temperatures in this discussion but they, of course, have something to do with ratios...though maybe not as much as people seem to think. Temperatures in the snow growth region are much more important and surface temperatures only effect densities once they exceed 32.0F. If you are below freezing at the surface, the only things that will effect the density is wind and temperatures aloft. It is not uncommon to get a wet snow with cold surface temperatures if the temperatures aloft are warming...likewise you can get a fluffy snow with temperatures of 32-33F if temps aloft are quite cold. In synoptic storms, ratios generally increase throughout the storm...starting off dense and ending fluffy. The cause is warming temperatures aloft in the first segment (southerly wind component) of a synoptic storm will generally cause lower ratios as those snow-growth region temperatures creep up toward freezing; while on the backside of a storm system ratios generally go up as the wind shifts to the north and the snow-growth region cools back towards that -12C to -18C temp range.
I am certainly rambling now and will end this post by repeating that snow measuring is not an exact science. There are a lot of factors at play but all we can do is try our best, in the name of science, to get the most accurate measurements that we can.
I look forward to continuing this discussion and again, thanks for the great points raised in this thread by Tony and JSpin.
-Scott
