Regional average annual percentages of homogeneous snowfall stations exceeding the 90th percentile for the Midwest region

Regional average annual percentages of homogeneous snowfall stations (Kunkel et al. 2009c) exceeding the 90th percentile for the period of 1900-01 to 2006-07 for the 8 states in the Midwest region. The snowfall percentile threshold for each station was calculated using the base period of 1937-38 to 2006-07. The percentage of stations exceeding the threshold for each region is calculated by dividing the number of stations in the region above the threshold by the number of active stations each year. The thick black line is an 11-year running mean of the percentages, and the dashed line is the number of active stations. Based on COOP data from the National Climatic Data Center. Only stations with less than 10% missing daily snowfall data for the period 1930-2004 are used in this analysis. Furthermore, the stations used here passed a stringent quality control analysis using expert judgment. Since 1985, the coverage of areas with snowfall exceeding the 90th percentile has been low.