The changing nature of severe snowstorms in the U.S

Although temperatures in the U.S. have increased more than 0.7⁰C since 1900 and the rate of warming since 1980 is approximately three times greater, the frequency of severe snowstorms has increased in some parts of the nation in recent decades. These storms often result in loss of life and economic losses in the millions and sometimes billions of dollars. The human and financialimpacts of the most severe snowstorms makes it important to understand how their frequency has varied and changed over the past 100+ years in an environment of warming temperatures. This study involved the analysis of snowstorms in the contiguous U.S. since 1900 to identify the 50 most severe storms in each of six climate regions in the eastern two-thirds of the nation. In some regions of the country more than half of these storms have occurred since 1980, while in the southern U.S., the frequency of these storms has decreased in recent decades. Conditional probability analysis is used to understand the relationship between anomalously cold and wet seasonal conditions and the frequency of severe snowstorms. In some regions these storms are most likely to occur during seasons that are unusually cold and wet, while in other regions the frequency of severe snowstorms has been little affected by the anomalous warmth experienced in recent decades. An assessment of temporal changes in the 50 biggest storms also provides insights into regional differences in the most common times of seasonal occurrence.