CIRCULATION PATTERNS AND TEMPERATURE FIELDS ASSOCIATED WITH EXTENSIVE SNOW COVER ON THE NORTH AMERICAN CONTINENT

Abstract

Weekly snow cover areas, derived from the NOAA/NESS Northern Hemisphere Digitized Snow and Ice Cover Data Base, were correlated with weekly temperature anomalies across the United States and with weekly 700-mb geopotential heights over the North American sector. The correlations were computed for snow cover across the entire North American continent as well as the western and eastern United States for the winters 1966–67 through 1979–80. Extensive snow cover is associated with negative temperature anomalies across most of the continental United States. The strongest relationship occurs along the eastern flank of the Rocky Mountains from the Canadian border to the central Great Plains and reflects the southward movement of cold arctic air masses toward the Gulf of Mexico. An anomalous trough over the western part of North America is responsible for extensive snow cover in the winter. The surface storm track is displaced southward during winters with heavy snow cover, with cyclones occurring more frequently in the southern Plains and southeastern United States. Moist Gulf of Mexico air advected northward by the southerly flow aloft is an important prerequisite condition for the occurrence of extensive snow cover in the eastern United States during the first half of winter.