Relationship Between Winter Snowfall and Summer Droughts in the Northern Great Plains of North America

The relationships between snowfall/snow cover and growing-season drought conditions are not, generally speaking, well understood. While numerous studies have demonstrated that Eurasian snow cover/snow depth affects the strength of the Indian/Asian summer monsoon, a connection between North American snow and drought has not been definitively established. The impact of fall/winter/spring snowfall on growing-season droughts were examined using a one-degree grid spanning the northern Great Plains of North America (40° to 54° N; 95° to 113° W). Based on data from 1929 to 1999, the results suggest that the relationship between snowfall and growing-season drought is non-linear. It appears that the snowfall anomalies must exceed some minimum threshold before they have a significant impact on atmospheric circulation and precipitation during the following summer. The results also suggest that snowfall anomalies during the late winter/spring are more important for determining summer moisture conditions than snowfall anomalies during the early winter.