Tuesday, February 28, 2017

Is March Really Utah's Snowiest Month?

One of the odder claims that I've seen in recent years is that March is Utah's snowiest month.  Ski Utah suggested this in their recent blog post March Always Delivers the Snow.


Certainly March can be a great month for skiing, especially if you like the combination of a deep snowpack, longer days, and warmer sun, but is it really the snowiest?

If one is talking about snowfall, that's debatable.  Below is the average total snowfall and average daily snowfall (in parentheses) by month at Alta based on data from the Western Region Climate Center.  Based on total snowfall, January is a bit ahead of March, although the difference is probably not statistically significant.  Based on average daily snowfall, a metric that I prefer because it adjusts for the number of days in each month, the snowiest months are January and February, although again, the difference relative to December and March is very small.

November: 62.8" (2.09")
December: 80" (2.58")
January: 82.7" (2.67")
February: 75.3" (2.67")
March: 80.1" (2.58")
April: 60.4" (2.01")

Numbers provided at the Utah Avalanche Center site for the Alta Guard station are somewhat different, but tell a similar tale.

November: 70" (2.33")
December: 92" (2.97")
January: 94" (3.03")
February: 83" (2.93")
March: 90" (2.90")
April: 68" (2.67")

This data shows that snowfall at high elevations in the central Wasatch is remarkably consistent during the months of December, January, February, and March.  Arguing that one of these months is snowier than the others is simply not justified based on long-term records.

Now perhaps there are other metrics that one might consider, such as the number of days with 10" storms.  I haven't bothered to dig into that, but in my view, that does not equate to "snowiest month," which most meteorologist would base on snowfall.

There is one other myth worth discussing here and that is the alleged January snowfall minimum.  Again, that does not show up in long-term records.  It could be that January features more variability from year to year, meaning a more feast or famine snow climate, but in terms of average snowfall, it is in a near dead heat with the other months.  I leave the issue of variability for others to investigate.  I need to get back to my day job.

14 comments:

  1. I think it goes without saying that the Ski Utah article is mostly meant to address the issue that booking decrease significantly in the Spring. They're just saying, "Hey, we still get lots of snow thru the end of the March." You're right though, it's remarkable how consistent our snowfall is from December-March. November and April aren't all that far behind either.

    ReplyDelete
    Replies
    1. You are right, but I'm always in need something to draw you in :-).

      Delete
  2. If Jan. suffers from feast of famine (which seems correct based on my memory), perhaps March is more consistent and therefore deserving of the title "always delivers the snow." Because an average Wasatch month (Dec.-March) can fairly be described as "delivering."

    ReplyDelete
    Replies
    1. I knew I would have to eventually run the numbers. Indeed, March has the smallest standard deviation of monthly snowfall (about 30 inches) of Nov-Apr. The largest standard deviation is actually December (about 46 inches), not January (41 inches). So, "always delivers the snow" might be hyperbole, but March is more consistent on average. Of course, my main complaint is the conclusion that March "is Utah's snowiest month" as suggested by the article.

      All of this is fine and dandy, but I'd still take two Februaries instead of one February and one March...

      Jim

      Delete
  3. Some of the claims are good for a laugh. Here's one from Brighton:

    "Brighton lies in the Wasatch Mountain range, which sits right next to the Great Salt Lake. This geographical blessing means that an average 500 inches of deep, light powder falls each year. That is enough snow to cover a four- story building. Brighton is the recipient of the coldest, driest snow in the world. Our snow averages a mere 6% water content…compared to say, Whistler’s 15-20%"

    ReplyDelete
    Replies
    1. Well I hadn't seen that one before. I could write a book on this stuff (ha ha).

      Here's some reading for them:
      https://books.google.com/books?id=7XA2okHw_jsC&lpg=PT57&ots=B-IVujuoJb&dq=The%20best%20deep-powder%20skiing%20is%20not%20found%20in%20the%20lightest%20snow%20Lachapelle%201962&pg=PT57#v=onepage&q=The%20best%20deep-powder%20skiing%20is%20not%20found%20in%20the%20lightest%20snow%20Lachapelle%201962&f=false

      Delete
  4. Thanks for keeping facts factual! Any idea about Utah's wettest month (most SWE)? maybe with average warmer temps in March we get more water. Still not making it the snowiest month, but just a thought?

    ReplyDelete
    Replies
    1. January also has the highest SWE according to the data at Western Region Climate Center.

      Jim

      Delete
  5. Jim, How many years back do the numbers you provide above draw from?

    ReplyDelete
    Replies
    1. The data from Alta-Guard is from 1945/46 to 2015/16. The period of record for the data from WRCC is less clear and would require some sleuthing to hunt down. Although the web site says 1905-2015, that would be for any weather element and I doubt the snowfall observations extend back to prior than WWII.

      Jim

      Delete
  6. "I knew I would have to eventually run the numbers. Indeed, March has the smallest standard deviation of monthly snowfall (about 30 inches) of Nov-Apr. The largest standard deviation is actually December (about 46 inches), not January (41 inches)."

    For that AltaGuard data since 1946 I have standard deviations of Dec. 45.4, Jan. 41.2, Feb. 29.8 and Mar. 35.4 inches, making February the most consistent month.

    For Alta Collins since 1981 (probably cleaner data), I have standard deviations of Dec. 43.8, Jan. 43.2, Feb. 29.3 and Mar. 34.9, same result.

    "There is one other myth worth discussing here and that is the alleged January snowfall minimum. Again, that does not show up in long-term records. It could be that January features more variability from year to year, meaning a more feast or famine snow climate, but in terms of average snowfall, it is in a near dead heat with the other months. I leave the issue of variability for others to investigate. I need to get back to my day job."

    Really, this myth is so persistent that I would greatly appreciate a definitive opinion from Jim S on the subject. I've looked up those standard deviations before. I've also been through the Alta Collins daily snowfall posted on the Alta website since 2005.

    Consecutive snowless day streaks at Alta Collins since 2005:
    Dec: 11,9,8,8,7,7,6,6,6,5,5,4,4,4,4,4,4,3,3,3,3,3
    Jan: 11,10,9,9,8,8,8,6,5,5,5,4,4,4,4,4,4,3
    Feb: 10,10,9,7,7,6,5,5,5,5,4,4,4,4,4,3,3,3,3,3
    Mar: 12,11,10,9,9,8,7,6,6,5,5,5,4,4,4,4,3,3,3,3

    I don't see a dime's worth of difference among those four lists above.

    I would appreciate your opinion of this data or any other metric you might think would be better to measure the incidence and severity of dry spells among the four winter months December - March.

    ReplyDelete
    Replies
    1. This comment has been removed by the author.

      Delete
    2. Ah Tony, I've been waiting for you to weigh in. Thanks for sharing these numbers. Chances are we used the same data for AltaGuard, so perhaps my statement that March had the smaller standard deviation was an error made in haste.

      On the January drought, I think it is a classic case of confirmation bias based on anecdotal impressions. In other words, it doesn't really exist. You won't hear anyone talking about the "March Drought" over the next few days as they will all be riding their mountain bikes and not worrying about it.

      Jim

      Delete
  7. Exactly! You will hear ME talking about the March drought because next week is my timeshare week at Snowbird!

    I believe SLC residents remember the January droughts most because they are nearly always accompanied by inversions and particulate pollution.

    In my case tracking ski seasons, I tend to remember December droughts the most because they severely delay opening of ski terrain. They are also the scenario that slash skier visitation (even later in the season due to bad publicity) and hurt the bottom line of ski areas most severely.

    ReplyDelete