If we look at the average temperature at Alta, for example, the largest outlier is not this year, but December 1980 – January 1981 (hereafter just 80–81).
There's a lot of missing data in the record for Alta, so I thought it might be wise to look at another site, in this case, Silver Lake Brighton. Indeed, it is 80–81 period that is the warmest on record.
The large-scale patterns for the two periods are actually pretty similar. 80–81 featured a western North American ridge and a deep North American trough.
The pattern is similar in 14–15, although it's not quite as amplified over the continental U.S.
So, it was a warm December to January period this year, but there has been warmer. Perhaps not surprising giving the strong ridging, the snowfall in 80–81 was also low, totaling 107 inches for the two months at Alta-Guard, just a bit more than the 102 inches observed this year.
A number of people have asked me if I think the bad snow years of late are a long-term trend. I don't think that they are for a couple of reasons. One is that there is a lot of variability in the climate system, so we need to expect some bad years and strings of bad years. Such years are in the instrumented record, as well as tree-ring reconstructions. A second reason is that although the warmth of this December–January and its impact on lower and mid elevation snow are consistent with the emerging long-term warming trend, the warmth this December–January has also been strongly accentuated by the anomalous ridge. In other words, what we have seen this year is primarily a reflection of the upper-level ridging and secondarily a reflection of that upper-level ridging occurring in a warmer world.
Whether or not climate change is increasing the variability in the climate system and perhaps increasing the likelihood of extremes like this year remains an open question being investigated by climate scientists today, and perhaps the subject of a future post.