U.S. snowfall analysis:
Less for the Northwest, an earlier start on the Plains

Despite recent headline-grabbing bouts of snow and ice in Seattle and Portland, the Pacific Northwest region overall gets less than half the snow it did 50 years ago, according to a new analysis by Daria Scott (University of Delaware) and Dale Kaiser (Oak Ridge National Laboratory).

The work was presented on 13 January at the annual meeting of the American Meteorological Society in Seattle. “While global and regional changes in overall precipitation have received much attention . . . relatively few studies of snowfall trends across the globe have been undertaken,” note the authors. Scott and Kaiser examined data for the October–May snow season between 1948 and 2001 at a total of 217 U.S. sites, all north of 35°N.

The most dramatic and consistent changes were found across the Pacific Northwest. There, the average number of snow days, the length of the snow season, and the average seasonal snowfall all dropped significantly, the latter by about 60% during the study period. Two belts across the north-central and northeast U.S. showed contrasting results. From roughly Colorado to Minnesota, the snow season now begins as much as 20 days earlier than in the late 1940s, with some evidence for heavier overall amounts. The lake-effect belts of lakes Ontario and Erie also show signs of increased snowfall. From roughly Missouri to the mid-Atlantic, the snow season begins up to 20 days later on average.

One finding was consistent nationwide: no U.S. regions saw a significant trend toward a later end to their snow season, while many trended toward an earlier end. Scott and Kaiser’s work was sponsored by the U.S. Department of Energy.