We're now into early March and the runoff prognosticators must be getting nervous. We had a bad snow year last year and as things stand today, this year is looking marginal too. Most drainage basins in the upper Colorado and in the Great Basin are running at less than 90% of average, and many are running at 75% of average.
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| Source: NRCS |
In the central Wasatch, the current snowpack SWE is at or just above last year, as indicated by the Snowbird (Little Cottonwood), Mill-D (Big Cottonwood), and Thaynes Canyon (Park City) SNOTELs.
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| Source: Colorado Basin River Forecast Center |
The fact we are so close to last year, yet this year doesn't seem to be as bad of a ski season, illustrates that you can only glean so much from total accumulated snowfall during a season. When it comes and how it comes really matters. This year, we had more snow during the early season, whereas last year we suffered mightily until late January and then caught up with a couple of big storm cycles.
I don't have a crystal ball capable of anticipating whether or not we will get into the stormy period that is needed to help us catch up and obtain an average end-of-year snowpack. The trough coming in later this week and weekend will help the southwest some, but what is sorely needed is a major pattern shift or a major storm cycle like the 2001 Hundred Inch Storm. At Snowbird, for example, we need about six inches of SWE just to catch up to average snowpack for this time of year. Making up ground like that is not impossible, but the odds are decreasing markedly as we move to later and later in the cool season.
Any theories as to why we have this big ridge two years in.a row?
ReplyDeleteThat's not really my area. That being said, sometimes there is a cause, and sometimes it's just the way the randomness in the atmosphere works out.
DeleteOne thing worth noting is that apparently the NRCS is now using median values (from the 1981-2010 period), instead of 30-year mean values to represent the "normal" precipitation and snowpack as was done in the past. Since the median values are generally less than the mean, this makes the resulting percentages of normal somewhat higher using the new method. I am not sure how much difference there is (I have heard maybe around 10%), but in most cases the percentages would be somewhat worse based on the traditional method.
ReplyDeleteThe average and median are plotted in the figures in this post, so you can have a looksee.
DeleteIt does look like the 78% for Snowbird is based on the mean and not the median (it would be closer to 90% of the median). Interesting. I thought that they had switched to using the median for snowpack percentages but I guess not at least for the basin map (also at http://www.wrcc.dri.edu/snotelanom/basinswe.html where it is labeled percent of "average").
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