The Association between Extremes in North American Snow Cover Extent and United States Temperatures

The association between satellite-derived North American snow cover extent and United States winter (December, January, February) temperature is examined. The results indicate that winter months evidencing extreme positive (negative) values of North American snow cover extent are associated with below- (above) normal temperatures across the majority of the United States. The area evidencing the largest temperature departures during both positive and negative North American snow cover extremes is located across the central United States, roughly from the Dakotas south through the southern plains, and from the Rocky Mountains east to the Mississippi Valley. This area is collocated with the largest variations in snow cover frequency. No consistently strong association is indicated east of the Appalachians or west of the Rocky Mountains. During December, strong 500-mb height anomalies are collocated with the area of maximum snow cover frequency deviations and the largest temperature departures. This is not the case in January and February. During these months the snow cover frequency and temperature anomaly fields are not in close proximity to strong areas of 500-mb deviations. Evidence is presented to suggest that continental snow cover anomalies produce remote temperature perturbations away from the area of local snow cover variations, through the large-scale modification of air masses. In addition, a brief climatology of North American snow cover is presented.