Eastern Snow Density, Snowfall Measuring Methods

J.Spin":1d9ikirb said:
I wanted to follow up on this statement, because Tony mentioned it in an email discussion with Fred Lavenberg, who is involved with the data collection at the Mt. Mansfield Stake. Although I’d never picked up on it myself, Powderfreak, who is fairly attentive to what is reported at the stake has mentioned the following:

At the Mt. Mansfield Stake data archives on SkiVT-L, one can pull up the daily snowfall reports associated with the stake, and here are the numbers of days with double digit snowfall indicated for each of the past four seasons since we’ve been back from Montana:

’06-’07: 1
’07-’08: 3
’08-’09: 0
’09-’10: 1

So essentially those data indicate that the upper elevations of Mt. Mansfield pick up greater than 10 inches of snow in a 24-hour period roughly once per season. We’re not even talking about a foot of snow here; these are just the number of times per season that the report hit 10 inches. I’d think for anyone that has spent much time skiing on Mt. Mansfield or has even kept up on the trip reports that come out of there, that sort of frequency seems ludicrous.

-J

Great find, Jay! For years I've wondered why we can't get double digit snowfall reported at the stake but still can't come up with the answer. We all know it snows 10" or more in a 24 hour period up there quite often throughout the season... I've got plenty of pics to prove it but I think the more telling point is comparing the stake numbers to the NWS weather forecast office at the Burlington airport (WFO BTV).

I have copied your numbers from the above post regarding frequency of double digit snowfall at 3,900ft on Mansfield... and then added the number of days the Burlington Airport (333ft elevation) recorded double digit snowfall in a 24 hour period by combing through the BTV climo F-6 forms. The results are startling given the fact that Mansfield averages twice as much annual melted precipitation and 3 times as much snowfall.

Frequency of double digit snowfall in a 24 hour period:
Season: Mansfield... Burlington Airport
’06-’07: 1... 2
’07-’08: 3... 2
’08-’09: 0... 0
’09-’10: 1... 3

*On my home computer I only have the most recent year's spreadsheet of Stowe's daily snow tally and during the '09-'10 season the ski resort recorded 6 days with 24-hour double digit snowfall on the upper mountain (which seems to make a heck of a lot more sense to me given BTV had 3). Since I do not have the '08-'09 daily tally I can't say for sure how many days we recorded double digit snowfall, but I do know that opening day November 20th, 2008 we reported 10" at 6am (J.Spin had at least 8" that morning at his house)... so there was at least 1 day (probably a bunch more, given the 349" seasonal total that year).

Overall though...how is it possible that in the past 4 seasons, the very low elevation Burlington airport in the Champlain Valley has recorded 10" or greater (during a 24 hour calendar day) 7 times, compared to only 5 times on the summit ridge of Mount Mansfield? That right there should raise some red flags regarding the snowfall measurements up there.
 
Comparing the stake numbers to some of the biggest powder days I can remember, it is startling just how low the stake numbers are during the big storms. Here are a few memorable ski days and their associated stake accumulations:

March 4, 2006... a large and un-forecast meso-scale upslope snowfall event that included the Champlain Valley, Western Slopes, and northern Green Mountain Spine resorts. Snow began during Friday evening, March 3rd, and continued through Saturday, March 4th. The majority of the snow fell overnight and during the morning of the 4th. Thus, one would expect a good stake measurement at 4pm on the 4th.

Here are the storm total accumulations reported by various outlets as the snow was winding down on Saturday afternoon:

BTV Airport... 14.2" (330ft elevation, 20 miles as crow flies from Mansfield summit)
Nashville...20.2" (850ft elevation, station is 7 miles as crow flies from Mansfield summit)
North Underhill...18" (near 1,000ft elevation, only 3-4 miles from Mansfield summit)

Code:
PUBLIC INFORMATION STATEMENT
SPOTTER REPORTS
NATIONAL WEATHER SERVICE BURLINGTON VT
227 PM EST SAT MAR 4 2006

********************STORM TOTAL SNOWFALL********************

LOCATION          STORM TOTAL    TIME/DATE    COMMENTS
                     SNOWFALL       OF
                     (INCHES)   MEASUREMENT

...CHITTENDEN COUNTY...
   NASHVILLE             20.2   100 PM   3/4   NWS EMPLOYEE
   NORTH UNDERHILL       18.0   100 PM   3/4   NWS EMPLOYEE
   WESTFORD              16.2  1105 AM   3/4   NWS EMPLOYEE
   JERICHO               15.0   842 AM   3/4   SPOTTER
   SOUTH BURLINGTON      14.2   100 PM   3/4   NWS OFFICE

Mansfield Stake...12" in 24 hours (3,900ft elevation, see link below).

http://list.uvm.edu/cgi-bin/wa?A2=i...5AB297785C8&Y=braaten.scott@GMAIL.COM&P=66101

*It should be noted that the depth on March 3rd, 2006 was 67" and on the 4th it increased to 79"...12" of NEW snow and a 12" gain in snowpack. This was an incredibly fluffy snowfall so a good deal of settling would be expected. I am always skeptical when the amount of snowfall equals the exact amount of the rise in the snowpack.

So for starters, somehow 14-20" of snow was measured by NWS employees in Chittenden County (Mansfield makes up the eastern Chitt County border) at elevations of 1,000ft or less. Meanwhile, only 12" was recorded over 3,000 vertical feet higher than the other reporting sites. In reality, I bet the storm total was more like two feet on the upper mountain. Based on J.Spin's email to skivt-l that day, it appears both Stowe and Smuggs reported 20" in the previous 24 hours which seemed to fit much better with what I was experiencing on the ski slopes.
Code:
It was really fun watching the snow totals.  The upslope accumulations as 
far as I can tell from the "official" skivermont.com website totals seemed 
to be (from north to south on the Green Mountain spine):

Jay: 28 inches
Smugg's: 20 inches
Stowe: 20 inches
Bolton: 30 inches
Mad River: 8 inches
Sugarbush: 4 inches
Middlebury: 3 inches
Killington: 0 inches
Okemo: 1 inch
Further South: all 0 inches
http://list.uvm.edu/cgi-bin/wa?A2=i...5AB297785C8&Y=braaten.scott@GMAIL.COM&P=73483

Here are two pictures to show depth... first one is my buddy Dave literally drowning in the deep snow. Second picture is of myself.

Dave%20deep3.jpg


I'm 6'3" and that is the deepest 12" I've ever skied ;)

Scott%20DEEP.jpg


The bottom line... the stake did not accurately represent the amount of new snowfall during this storm system and might have under-reported the snowfall by 50% as I honestly believe there was at least two feet up there (which jives well with other northern Vermont resorts based on J.Spin's skivt-l email posted above).

_________________________________________________________________________________________________________

The next storm I'd like to touch on is the Valentines Day 2007 storm...which I also believe the stake under-reported by close to 50%.

Again, the Burlington airport somehow managed to receive more snowfall than Mansfield 3,500 vertical feet higher. During this storm, BTV shattered it's 24 hour snowfall record with 25.7" in 24 hours. Meanwhile, the stake only reported 24" at 4pm on the 14th with nothing else on the 15th even though the heaviest snow of the storm was ongoing at 4pm and heavy snow continued into the early morning hours of the 15th.

http://list.uvm.edu/cgi-bin/wa?A2=i...57A2416503&Y=braaten.scott@GMAIL.COM&P=172008

Here's what the ski areas reported...widespread 3-5 foot totals in the upper elevations and that jives well with spotter reports down in the lower elevations (below 1,500ft) of 26-40". From the NWS statement following the storm, most mountain communities (such as the village of Stowe) received 30-36" and again, those totals are relatively low elevations compared to over 3,000ft on Mansfield. I think that lends credit to some of the 3-4 foot totals reported by the ski areas.

skivermont snow report.jpg


And lastly, here is a picture I took of my friend, Tyson, on February 15th in the Stowe Backcountry. This picture was taken less than a quarter mile from the Stake.
Tyson is 6 feet tall AND he has his skis on which are providing some sort of float/support. Now to be THAT deep in the new snow with your skis on, I gotta believe the actual storm total was at least 3 feet, if not 4 feet+. We were actually quite concerned with becoming over-turned (drowning?) in all that snow and that doesn't happen in just 2 feet of snow.

TysonWalking_edited.jpg


I'm not exactly sure why, but I honestly believe that the Mansfield stake data is consistently low (and significantly so at times) during major winter storms. Wind is likely the factor, packing the air out of the snow (no fluff factor) as well as leading to the snow measuring cylinder to under-catch snowfall. Either way, I really do not think that adding up the daily 24 hour "NEW" snow values from the Mansfield stake co-operative observing station represents an accurate picture of real snowfall on Mount Mansfield (and Stowe).
 
powderfreak":w65nph9x said:
(I'm not sure I've ever heard anyone question a Western mountain's snowfall)
You must not have read much of my commentary over the years. :lol: The most misleading info is what I call the "brochure quote," which appears repeatedly in marketing literature, and even though it is never backed up by actual data, is quoted without question by the ski mags and eventually seeps into the public consciousness. The worst offenders in this regard are the "brochure quotes" of 400 at Big Sky and 500 at Powder Mountain, both of which are overstated by close to 150 inches!

The more common practice, both East and West, is to measure as high as possible on the mountain, thus compiling legitimate data that is not necessarily representative of 75+% of the ski terrain. This is what Jay Peak has been doing for the past decade, but since they still maintain a lower mountain figure, I collect that at the end of the season and average it with the the upper one. I do the same for Kirkwood. A variant of this situation occurs when there is good long term data at a mid-mountain location, but in recent years the area has added an upper location and in-season marketing quotes are always for that upper location. Since the mid-mountain data is still being collected and I can get it, I continue to use that. This is how reporting is done at Alyeska, Jackson Hole and Park City.

Proper snow measurement needs to be done from a sheltered location, and that does exclude the very highest locations in places like Mammoth, Bachelor, Whistler and Alta/Snowbird. By contrast the tree line is very high in Colorado and most of the Colorado areas take advantage of that and measure ~3/4 of the way up their elevation range. My practice is to insist upon quoting the exact elevation where snow is measured (averaging if necessary), then also showing the elevation range of the ski area and letting the readers draw conclusions accordingly.

powderfreak":w65nph9x said:
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).
I do collect some snow depth info and have compared max base depth to total season snowfall. The highest figures (no surprise) are Mt. Bachelor at 40% and Mammoth at 39%, as these areas combine high density coastal snow with excellent preservation. For Alta/Snowbird that ratio is in the 25-28% range, as is true for most of Colorado.

powderfreak":w65nph9x said:
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.
This is IMHO a key difference between East and West. In most of the West the temperatures aloft during winter storms are nearly always colder than those on the ground. And during prolonged storms there is a strong tendency for density to decrease over time. The study last year by someone at University of Utah of Alta's records noted this trend and considered it a key contributor to the quality of Alta's skiing: first depositing a layer of relative dense snow, followed by fluffier powder on top of it.

I do hear occasionally of "upside down storms" that end with heavier snow or rain in the PNW, but that is more rare in my Sierra or even SoCal experience and nearly unheard of in the Rockies.
 
Both the eastern snow density and snowfall measuring method discussions are likely to be valuable for future reference. The discussions are intertwined and somewhat related so I have chosen to rename rather than split the topic, hopefully making those future references easier.
 
powderfreak":2ejc31nl said:
Again, the Burlington airport somehow managed to receive more snowfall than Mansfield 3,500 vertical feet higher. During this storm, BTV shattered it's 24 hour snowfall record with 25.7" in 24 hours. Meanwhile, the stake only reported 24" at 4pm on the 14th with nothing else on the 15th even though the heaviest snow of the storm was ongoing at 4pm and heavy snow continued into the early morning hours of the 15th.

http://list.uvm.edu/cgi-bin/wa?A2=i...57A2416503&Y=braaten.scott@GMAIL.COM&P=172008
Scott, thanks for your incredibly thorough and informative input, I'm likely going to read your text at least a couple more times as I think about all the information.

A note on your SkiVT-L links above: I've found that due to the way SkiVT-L is set up, if one is logged into the UVM listserv when they grab a SkiVT-L link, that link brings the viewer to the listserv login page instead of the actual post - you'll see the braaten.scott in the web address above. I always log out from the listserv to grab links, then it seems to bring the viewer right to the post. It also looks like you can simply delete the "&Y=braaten.scott%40GMAIL.COM" from your links to produce:

http://list.uvm.edu/cgi-bin/wa?A2=ind07 ... 3&P=172008

which brings one right to the post in case you want to edit the ones you used here.

Thanks again for all the great information; you are definitely in a great position to compare/discuss the discrepancies between the snowfall recordings at the stake and the resort.

-J
 
I finished updating my regional web pages to reflect 2009-10 snowfall data I received from 81 areas. Season Summary for those: http://bestsnow.net/summ10.htm

On the intro to the Eastern page I expanded my discussion about snow reporting from the Mansfield Stake to reflect the additional info from this thread: http://bestsnow.net/eastnet.htm

FYI total number of areas I have with snowfall data is now 102 with the addition of Brundage, where I skied with NASJA March 21-22. http://bestsnow.net/nrocnet.htm
 
A couple of months back when we were discussing Tony’s data on snow density at various ski areas, I generated a plot of the numbers in his revised table for an easier visualization of the peak and distribution of the snow density. I never got around to posting it, but in response to some discussion in the Sugarloaf expansion thread over at AlpineZone, I decided that it would be nice to display the plot for those that might not want to mull over the table:

skiareasnowdensityvsfreqency.jpg


To generate the plot, I took Tony’s numbers from his revised table, normalized the snow density frequencies for each ski area using a value of “1” for the peak snow density (so the peak values could be compared easily on the same plot), then added a moving average trend line (period = 2) to smooth out the double/jagged peaks. The above plot shows the three trend lines, with the peaks indicated. The peaks are just about what you’d expect from inspecting the numbers in Tony’s table, and you can get a quick sense of the relative snowfall distributions.
 
I believe that my original chart is closer to the mark than the revised chart due to the container method understating both new snow and water content. It's also quite relevant that 24% of Mt. Mansfield winter precipitation is in the form of rain or mixed (40+% water content) vs. 1% at Mammoth and 0% at Alta. I do understand that most skiers would prefer density distribution compared over snow rather than water, so that's why I created the table showing it both ways.
 
Tony Crocker":ljg38jqk said:
I believe that my original chart is closer to the mark than the revised chart due to the container method understating both new snow and water content.
Based on our current understanding of the causes of the decreased snowfall reporting at the Mt. Mansfield stake, the amount of correction that needs to be made to the original table appears to come down to whether the snowfall deficiency is caused by 1) a portion of the snow simply not being captured by the container at all (in this instance, both the snow and it’s associated water content are excluded from measurement, there is no effect on snow density calculations, and thus no correction to the numbers in the table are needed), and 2) excessive settling of the snowfall due to the 24-hour collection interval/daytime heating/melting (if the entire snowfall deficiency was derived from this cause, then the maximal correction would be needed). With the information at hand, I’d be interested in hearing why you feel that cause #1 accounts for the lower snowfall numbers at the stake.

While it is very possible that the amount of snow captured by the gauge on Mt. Mansfield is reduced relative to what would be captured on an open, flat snow collection surface like a board (as I have observed in comparisons with my own gauge and boards), we don’t actually know how much of a factor it is for the specific gauge and location in question. I would argue that this issue is probably not the major source of the snowfall deficiency at that specific setup, and that the corrected table is a better depiction of the snowfall in the higher elevations of Mt. Mansfield for the following reasons:

1) Regardless of whether snowfall is being missed by the gauge or not, whatever does fall in the gauge is still going to settle over the course of a day. Thus, in order to pick up the 230 inches of 24-hour/daytime heating/rain-settled snowfall per season that is reported at the stake, substantially more snow than that has to fall. How much more? 10%? 20%? 30%? Higher? The rate and extent of the settling is going to vary with the density of snow, but from personal experience, I would say that even 30% settling isn’t surprising for some of the very dry snow that we receive in Northern Vermont, and numbers like that could account for a large part of the discrepancy in snowfall reporting between the stake and the ski resort. Although I don’t specifically monitor rates of snowfall settling over 24-hour periods for my own analyses in Waterbury, using the details associated with my snowfall observations can allow for some settling estimates. Here are some observations from a storm that started on Thursday, December 31st, 2010:

On Saturday, January 2nd, 2010 at 10:30 P.M. in the evening, my observations at the house indicated that we had just picked up 6.6 inches of 3.2% H2O snow in the previous 6 hours, the temperature was 11.7 F, and there were 19 inches of snowpack at our back yard stake. The next morning, Sunday, January 3rd, 2010 at 7:00 A.M., I made my next set of observations. The temperature was 9.5 F, an additional 5.1 inches of 5.9% H2O snow had fallen on the snowboard, and the snowpack at the stake was 21 inches.

Without any settling, the expected depth of the snowpack at the Sunday morning observation would have been about 24 inches (19 inches + 5.1 inches), but it wasn’t; a full three inches of snow had been lost in that 8.5-hour period. Based on the air temperatures recorded along with the observations, the snow was clearly not melting, and the winds were not strong enough that they were packing the snow, so the loss appears to be due to settling. The observed settling at our stake was presumably not coming from the 5.1 inches that had just fallen though, since during the 8.5 hours in which it fell, it should have settled just like the 5.1 inches that had simultaneously fallen on the snowboard. However, at our back yard stake, that new 5.1 inches of snow had accumulated on top of the 6.6 inches of snow that had fallen in the previous six hours. If one assumed that all the observed loss in potential snowpack depth came from that underlying 6.6 inches of snow that had fallen in the previous round of collection, it would represent a loss of 45.4% due to compaction.

To further distribute the settling into more of the snowpack though, we can assume that the three lost inches came from all the snow that had fallen since the start of the storm on Thursday evening, December 31st, 2010 (12.9 inches). Even that calculation puts the loss of snow at 23.3%. However, that number is probably low with regard to how much settling actually occurred for the whole storm, because with the initial rounds of snowfall we are now getting back to a period more 48 hours before the measurement, and the snow had probably done some of its own settling prior to the compression from the new snow on top. Since I have several rounds of detailed snowfall and snowpack observations from the storm, it’s possible to go back and determine the additional snowpack settling from each interval. That gets pretty tedious though, and it’s fairly easy to get a sense for the settling with a look at the snowfall and snowpack change over the course of the entire storm… or even with the inclusion of previous storms.

Back on Monday the 28th and Tuesday the 29th of December, we’d also had another 9.1 inches of snow from a different storm, so one could also think about including that into the settling calculations. But, the farther back in time and deeper into the snowpack one goes, the more the snow will have already settled, and the less and less it plays into the settling seen in the most recent snowfall. The settling process is clearly dynamic, but if one were to try to determine settling for those specific 6.6 inches from the storm above, the amount of settling is presumably going to fall somewhere in the range of percentages that I mentioned. Add to that the settling that the previous rounds of snow had already undergone before new snow had fallen on top, and one can at least get a sense of what might be going on over the course of 24 hours with these types of dry snow.

To provide some perspective on the overall settling during a longer timeframe, let’s look at the change in snowpack over the period. On the morning of Monday, December 28th, before either of those two storms came in, the snowpack at the back yard stake was at 7 inches. Since there had been some warm weather near the Christmas Holiday, the surface of that snow should have been pretty solid and not subject to much compression, so it’s a convenient place to begin an analysis of snow settling. In the ensuing several days, 27.1 inches of snow fell at the site, and the snowpack at our stake wound up at 21 inches. That represents a 14-inch increase in snowpack from 27.1 inches of snowfall. Roughly half (13.1 inches, 48.5%) of the “potential” snow depth from my six to twelve hour snowfall observations was lost in those several days.

And, let’s not forget that the settling taking place during that period was happening in a consistently cold and calm location, and that any heating, rain, or winds would further increase the settling. Even snow that is settling relatively quickly is still doing so on a timescale that people aren’t going to perceive, so I don’t think people really appreciate just how much settling goes on with the very dry snow that we get in the upslope regions. I’d argue that the settling that takes place in fallen snow of this type over the course of 24 hours, especially with other insults to the snowpack thrown in, can be quite substantial.

2) Another argument I’d make to suggest that the revised table is actually more representative of reality than the original one, is something I’ve mentioned previously in this thread. This point is based on the typical snow density used by the NWS and other forecasters for the Northeast U.S (1:10 – 1:12 H2O:snow, or 8.3% - 10.0% H2O). With all the dry upslope snow that Mt. Mansfield receives on top of the standard synoptic 8-10% H2O snow, one would expect the overall density of the snowfall to be below this range (less than 8% H2O), not at the top of it (~10% H2O) as the original table suggests.

3) Finally, I decided to calculate the average density of the snow that fell at my own house last season, because I was pretty sure that even at our spot down low in the valley, the mean snowfall density was below the 8-10% H2O range. Using the amount of snowfall and associated liquid for each storm, and weighting by the amount of snow, the calculation revealed an average snowfall density of 7.5% H2O for my location in the 2009-2010 season. In this calculation I was able to incorporate 121.5 (95.1%) of the 127.7 inches we received last season at the house. For the remaining 6.2 inches (4.9%) that fell, the snowfall either occurred outside the November through April timeframe, or I lacked all the liquid data to perform the calculation. The storms and their associated data that were used for the calculations are shown in the table below to provide an overview of the type of events and densities that are involved:

0910stormssnowdensitytable.jpg


The 7.5% H2O number is the average (mean) value for the snowfall density, and it may not coincide exactly with the peak (mode)-style value that one would pull out of tables made up the way Tony has them, but the values should be close unless the distribution of snowfall density is very strange.

I would also argue that the mean density of the snow that falls (or at least the density of the snow that is measured) up on Mt. Mansfield at the stake is even lower. We’ve already discussed the relationship between snow density and elevation in this thread, and I think Powderfreak did a nice job of explaining why there shouldn’t be much of a difference in snow density at various elevations as long as all locations are under consistently sub-freezing conditions. The snow is created up in the atmosphere with a certain structure, and it’s that structure that determines the density to which it packs. Whether the snow finally settles at around 4,000’ up on Mt. Mansfield, or at around 500’ in my back yard, as long as other factors like wind or above freezing temperatures aren’t affecting the deposition, the snowfall should all have the same density. The problem is that above freezing temperatures do occur, even in the Northeast where winter temperatures are typically below freezing all the way to the valley floors. I’m sure everyone can relate to the experience of increasing snowfall density with decreasing elevation at ski areas - how many times does Whistler experience storms with powdery snow in the alpine and slush or rain at the base areas each season. I don’t think anyone believes that the same snow density is going to be recorded at both elevations. A perfect local example can be seen from this past season at Mt. Mansfield. On Thursday, February 25th, our family skied with Stephen and his children at Stowe, and I spoke specifically about the density of the snow with respect to elevation in my report from the day:

“The uppermost elevations were in the clouds, so visibility was low up there, but those areas also had the driest snow. The middle elevations were sort of that sweet spot where visibility was up, and the snow was still nice. The lower ½ to ¼ of the mountain had great visibility, but the snow was fairly wet, so off piste skiing wasn’t quite as easy as it is with our more typical Vermont fluff.”

It didn’t take a rigorous analysis of the fallen snow to know that the density varied quite a bit over the 2,000’+ elevation range that we were skiing. The precipitation we were seeing at the time told the same story, with reasonably dry snow falling on the upper part of Mansfield, and combinations of rain and wet flakes coming down at the base elevations (~1,500’). At the house, another 1,000’ below that, the precipitation had been entirely liquid as far as I could tell, so I have a hard time seeing how the density of the measured snowfall through that 3,000’+ elevation range would not show substantial differences. That snow may have been all the same when it formed up in the clouds, but due to surface temperatures it did not settle with the same density at various elevations down below. One can look at my table above and see the high density of the Winooski Valley snow associated with those storms at the end of February; there was even some rain and very dense snow in the second storm that produced an overall density of 20.2% H2O. Meanwhile, up at the Mt. Mansfield stake, the precipitation was all snow through those storms. With Mt. Mansfield being both north of our location and at a higher elevation, barring the effects of wind etc., it would have to be an extremely rare event indeed that would ever produce snow on the upper elevations of Mt. Mansfield that was denser than what we were simultaneously picking up at the house.

Based on the above data and discussion, with the caveat that average snowfall density may not exactly mirror the peak value obtained from a table like Tony has produced, it’s hard to see how the original table is a very realistic representation of Mt. Mansfield’s snow density. Even the snowfall data obtained from my house for the 2009-2010 season, which include a substantial amount of unusually wet snow that fell at the end of February, reveal a mean snowfall density of 7.5% H2O. So, for Mt. Mansfield’s average snowfall density for November through April to be at 7% H2O or even below that value should not be too surprising. Indeed, for the Mt. Mansfield gauge associated with the stake to still be measuring 230 inches of snowfall per season after accounting for both a failure to collect a substantial portion of the snow as you suspect above, and 24 hours of snow settling each day, then the resort observing a 333” snowfall average at that elevation is not too surprising.
 
I would think the straightforward way to test the effect of settling by measuring frequency would to have 2 snowboards (or containers) and measure one of them once a day and the other twice a day. The once-a-day measurements at the Mansfield Stake are common to many snow measuring sites. Their non-standard procedures that are likely to understate vs. other places are IMHO first, use of a container rather than a snowboard and second, measuring at 4PM vs. early morning. The container issue affects density very little, while the 4PM measurement logically would result in more settling in some cases than a morning measurement.

I agree with powderfreak's elevation comments due to Mammoth (with virtually no rain and much higher elevation) having similar snow density to Alpine Meadows and Stevens Pass in the Westwide Network snow data from 1979-1995.

Average snow density is usually determined by dividing total water by total snow, yielding 8.5% for Alta and 12.9% for Mammoth. While that method does not work in aggregate for the Mansfield Stake with 14% of precipitation being rain, now that I have sorted their data we could use that method by throwing out all precipitation events over 20%, thus excluding the rain and mixed. If you do that you get 9.9%, a number that makes sense to me. The distribution curve shows that Mt. Mansfield gets a similar proportion of very low density events as Alta. But we know there are very high density events also. So I'm not buying that the overall density average is 7.5%, which would be lower than Alta and in the range of some Colorado areas. Or perhaps the "settling" effect in Alta's 8.5% is similar to Mt. Mansfield's at 9.9%. With NOAA standards of measuring either once or twice a day (per Mt. Baker's world record), every snow site will have some settling in their data.
 
Some of the people involved with Stowe snowfall measurements (Powderfreak etc.) met with Fred Lavenberg yesterday, so I figured Tony would be interested in Powderfreak's comments from Wednesday, and Thursday. Basically everyone knowns that the snowfall numbers associated with the stake data are flawed, so they discussed that.
 
Basically, this is the way it has been done for 60 years and they know its flawed but no one wants to mess with changing what has a significant historical period of record because then you can't compare it with past years. I'm not sure how I feel about that.
This is precisely the problem. Fred has been very helpful to me over the years sharing this data, but tended to put me off when I first started making inquiries about low snowfall measurements several years ago. The 4PM measuring time was the only issue I knew about until JSpin and powderfreak got on the case here. I'm pleased to see that direct communication is now underway. Progress is more likely to be made dealing face-to-face with knowledgeable people on site like you guys than at long distance with a "pontificator from Southern California."
 
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