Friday, March 30, 2018

Your Parents Had More Powder Than You

Snowfall observations have been collected at Alta Guard for November through April since the 1945/46 season.  As noted in today's Utah Avalanche Center advisory, Alta Guard has measured 245" of snow since November, with 24.65" of water.  It does not appear that they will add to this total through the end of the month, which will result in the November to March snowfall being the second lowest on record, behind only 2014/15, when only 220.5 inches was recorded. 

Although I still consider 1976/77 to be the worst snow year on record for skiers, mainly because the early season snowfall was so poor (even worse than this year, see Deep Dive: How Unusual Is Our Snowfall and Snowpack This Season, posted 9 Feb 2018), that season is now ahead of this one from a November to March snowfall perspective, with 283.5 inches.  Nevertheless, this has been a remarkably dismal snow season and one of only 6 seasons with less than 300 inches of snow at Alta Guard from November to March.

2014/15: 220.5"
2017/18: 246"
1962/63: 265"
2011/12: 281.5"
1960/61: 291"
1976/77: 283.5"

Recent years have also been relatively poor within the period of record.  The 10-seasons from 2008/09 through 2017/18 have the lowest seasonal snowfall average with 339 inches.  In second place for a 10-year running mean is 1953/54 through 1962/63 with 359 inches.  If you want fat snow years, look to the 80s and 90s, with the peak 10-year average of 492 inches from 1988/89 through 1997/98. 

Sorry kiddies, but your parents had more powder than you.  Quite a bit more powder.  

I have been avoiding comments on the causes of recent poor snowfall years for a variety of reasons.  Perhaps the most important is that I don't think that we have done adequate research to understand the causes.  Don't label me a climate denier for saying that.  It is clear that our warming climate is decreasing the fraction of wintertime precipitation that falls as snow in the lower elevations of Utah.  It is also clear that it is affecting snowpack over Utah. 

However, the whims of the jet stream could also be playing a role, and probably a significant one.  Tree rings have been used to infer pre-historic climate over the western U.S. and illustrate that although 75 years seems like a long time for humans, it's really an inadequate sample of the climate variations that effect our region.  For example, tree rings have been used to construct streamflow for the Bear River and show much stronger (and longer) periods of drought than observed in the latter half of the 20th century. 
Source: DeRose et al. (2015).  Drought and pluvial (wet) periods illustrated by black and grey fill, respectively.  Note that this graph is smoothed to illustrate slower climate variability.
The plot above illustrates that there are slow variations in regional climate that can cause decadal (or longer) periods of wet or dry conditions.  The causes of these variations are not fully understood, but are at least in part related to variations in ocean temperatures and sea-ice coverage that I lack time to discuss here.  I suspect that recently poor snow seasons in the Wasatch partially reflects these variations.  

The long-term trends related to global warming are clear and their impacts on Wasatch snowfall and snowpack will continue to emerge during the 21st century.  However, along with these trends are slow variations in regional climate.  Understanding and predicting those variations is an important area of research and provides many thesis and dissertation topics for motivated students.  Beyond skiing, there are important implications for water resources and water resource management.  


  1. The years 1200 to 1300 are the major drought coinciding w the disappearance of the Anasazi.

    The first part of this century (i.e., after 2000) shows up as a mild drought in comparison.

    The "smoothing" is interesting as it shows the entire period since roughly 2000 as drought, where we had some really good winters, including 05/06, 07/08 and 08/09. While 10/11 was blessed, it was just 550 inches at Alta Guard, where the other good years were near or above 600 inches.

    This chart is the buzzkill I mentioned. We are due for a pronounced and prolonged drought period; worse than what we have experienced so far.

    All we can do is pray that hot and dry doesn't really get going while we are alive. Too, this natural cycle of wet and dry, where we are headed for dry, is occurring on top of the general warming trend climate change is bringing.

    NOW! is the time to PRAY FOR MORE SNOW and LESS WIND for next year.

  2. Tree rings do not correlate perfectly with snowfall. They are integrators of the overall climate each season. In addition, the trees sampled for the plot were taken from an area in NE Utah, not the Cottonwoods. Thus, one wouldn't expect good match with snowfall. I've swept such details under the rug. The key point is that slow variations in the climate system are to be expected in our part of the world, with persistent drought certainly possible.

  3. What does this mean for the Great Salt Lake? Can the lake survive the 21st century?

  4. Dear Professor,
    What is the 72 year average for Alta Guard, Nov-April?

    1. The mean Nov-April snowfall from 1945/45-2016/17 is 486 inches.

  5. I have heard this name before used in the other various ski related blogs I read but don't know much about it, the MJO, or Madden-Julian Oscillation. Does the MJO affect Wasatch snowfall? If it does, is it a weekly, monthly, yearly, or longer effect? I searched your blog records and did not find any posts about it. Have you written about the MJO before? If not, perhaps an MJO post in the future?


  6. A post on the decadal and longer cycles would be appreciated.