Cottonwood Canyon Snowfall Data

Tony Crocker

Tony Crocker

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Staff member
Stan":3vefrzqi said:
Since at least 1999 (when I first started going there) Alta's snow data has been from the Collins snow plot at about mid-mountain. I suspect that this location has been in use for a lot longer than that.
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Alta has averaged 613 inches since admin moved to Utah in 2004-05 vs. 522 in the 31 prior seasons. Coincidentally 2004-05 is the first season of high speed Collins and also the first season where Alta published daily snowfall data on its website. These facts led to my suspicions about a new reporting location.

However I know from numerous other examples that snowfall can run well above or below average for extended periods. I will eventually talk to Alta patrol, but they are not around at this time of year. So I've compared to Snowbird's patrol data, which has been consistently from the tram base for a long time. Alta/Snowbird tram base snowfall ratio during admin's 7 years is 123%, but it's 124% for the 7 years of lower snowfall before that, supporting Stan's view that the Collins site dates to at least the late 1990's. For the previous 22 years the ratio is 117%, and for the first 8 years of complete data for both starting in 1973-74 it's 99%. Somebody was doing something different before 1981-82, but it's hard to say if there was a change in the late 1990's.
 
I had left this alone for awhile but on my last visit to Snowbird I went into the snow safety office and one of the older patrollers knew that ALL of Snowbird's patrol data since the area started in 1972 is from the tram base.

Last week I recalled the Western Regional Climate Center data from Alta's base that I had used to analyze dry spells:
http://www.wrcc.dri.edu/cgi-bin/cliMONtsnf.pl?ut0072
This data is supposedly measured at 8,730 feet. What was interesting is that 33 months between 1979-80 and 1985-86 matched my Alta data within an inch or two. So I then suspected that the Alta Collins 9,600 site came into being starting in 1986-87. From then on my Alta data is consistently higher than WRCC's with no exact match months.

I finally reached a long time Alta patroller this week. He said the Alta Collins plot at 9,600 has been there since he arrived in 1979 and has been well maintained. He is not sure of the "quality control" of the ski area data before then. It turns out that the ratio of Snowbird to Alta snowfall is out of line precisely from 1973-74 through 1978-79. Since 1979-80 the ratio has never exceeded 95%. During those 6 prior years the lowest ratio is 94%, 4 of the 6 years exceed 100% and the top 2 are 115% and 116%.

WRCC is missing data from 1977-78 and 1978-79. It seems likely that they took data from the ski area from 1979-80 through 1985-86, then measured independently from 1986-87 onwards near the base at 8,730. The Alta patroller volunteered the observation that snowfall measurements even across the road at Alta can vary. Exact matches for a whole month, much less 25 or 30 months, means someone was sharing data. Since he was at Alta measuring at the Collins plot during that time frame, he presumes someone at the ski area was supplying that same data to WRCC.

My previous Alta dataset from 1966-67 was likely "apples and oranges" with a season annual average of 530 inches. 33 years of clean data since 1979-80 from Alta Collins 9,600 average 542 inches. The 39 year Snowbird tram base average remains at 462 inches. 2012-13 is not included in any of these numbers.
 
I was an Alta local during the 1978-79 season and can remember one particularly heavy snowfall week I believe February or March 1979, in a lifetime of skiing I have never seen better. Does anyone have the snowfall history available from this period, I’d be particularly interested to see how it stacks up against other years. I've already checked the Alta ski area and Western Regional Climate Center web pages, no luck. Thank you!
 
My data is only at the monthly level. There is nothing exceptional about February (102.5 inches Snowbird, 86 old Alta) or March (67.5 Snowbird, 71 old Alta) in 1979. An average winter month is about 90 inches at Alta and 80 at Snowbird.
 
It is surprising that it has taken so long to to sort out Cottonwood Canyon snowfall data.

Alta
As mentioned above snowfall has been measured at Alta Collins since 1980-81.

Sometime since 2013 Jim Steenburgh referenced UDOT measuring snowfall near Alta's base and directed me to this reference: https://utahavalanchecenter.org/alta-monthly-snowfall At that point I separated my data between Alta Collins and Alta Guard. The Alta Guard data does not have obvious mix-and-match red flags like the WRCC data, matching Alta Collins exactly for some years. However the ratio of Alta Collins to Alta Guard is 95% from 1981-1999 and 112% for 2000-2018. Steenburgh has no explanation for this but there seems to be a strong consensus that the Alta Collins data is very trustworthy. So with 38 years of data I'm going with that.

The Alta Guard data nonetheless has a lot of value going back so far and providing some historical perspective. Utah's snowfall record for the past 7 years is historically bad, with Alta Collins being over 2 standard deviations below average over that time. But this has happened before; Alta Guard was over 2 standard deviations below average for an 11-year stretch from 1953-1963. Both periods also include three seasons Alta Guard had less than 100 inches of snow before Jan. 1. There are only 9 such seasons since 1946, the others being 1980-81, 1986-87 and the record low 30.5 inches in 1976-77.

Note also that when this thread started in 2011, the prior 7 seasons at Alta had been the highest such period on record.

Snowbird
As noted before, Snowbird patrol has insisted every time I've asked that they only measure snow at the 8,100 foot tram base. Obviously Snowbird marketing does not like to use this number in-season, and by now it's fairly well established that whatever is quoted on the Snowbird website is not measured in any systematic and scientific manner.

However, Steenburgh and others often refer to a Snowbird SNOTEL at 9,600 feet. This is a good mid-mountain location and also at the same elevation as Alta Collins. It occurred to me that the new water content of snow at the SNOTEL could be compared to that at Alta Collins to get a good relationship between Alta and Snowbird snowfall. Alta's website displays daily snowfall and water content going back to 2004-05. To no surprise the two water content numbers are 96% correlated and the Snowbird SNOTEL averages 89.7% of Alta Collins.

In 2015 I revisited Alta patrol to pick up the Collins data including water content going back to 1980-81. This allows me to calculate Snowbird SNOTEL snowfall = Alta Collins snowfall x Snowbird SNOTEL water content / Alta Collins water content. This can be done on a monthly basis going back to the start of the Snowbird SNOTEL in 1989-90.

So now we have credible Snowbird measurements both at mid-Gad and the tram base. I now exclude tram base data before 1980, because it's not credible to be consistently measuring higher than Alta Guard during the 1970's. Both include May snowfall because Snowbird is usually open most of May while Alta is not. I also use the formula above to track Snowbird snowfall in-season as both Alta Collins and the Snowbird SNOTEL are updated daily.

Solitude
Via the Westwide Network, there is complete monthly data from Solitude's 8,000 foot base from 1993-2000 and scattered data for a decade before that. Since 2001 Solitude has been measuring from a snowier location at 9,400 feet. Average of these two sites is probably a good representation for overall ski terrain at Solitude.

Brighton
There was an independent site reported on WRCC in the backyard of a house across the parking lot from Brighton's base. Reporting became erratic around the time admin moved to Utah, so he drove me up there in May 2005. We saw the station, but reporting continued erratic and finally stopped completely at the end of 2010. I had not been motivated to contact the ski area directly in my original data collection in 1992-1995 as the WRCC site was nearly complete back to 1968. But this site would be an underestimate relative to the other Cottonwood areas measuring within their ski terrain. So in 2017 when I skied a day at Brighton during Iron Blosam week a patroller told me whom to contact.

2017 also piqued my curiosity because the unusual southwest flow that season resulted in Brighton reporting more snow than Alta. That information was posted as the season progressed but it took me until fall 2017 to get any prior years' data. The Brighton ski area measuring site is at 9,504 feet near Snake Creek and the data goes back to 2004-05. Despite the anomaly of 2016-17, that data is 92% correlated to Alta Collins and it is at a representative mid mountain elevation. I have renamed the old WRCC site Silverlake.

Updated summary snowfall stats are here: http://bestsnow.net/utahnet.htm
 
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