These monthly snow cover anomaly maps give an indication of how much monthly snow cover conditions varied from normal. The departure from average conditions is expressed as a standardized anomaly with respect to a 1972-1995 reference period mean and standard deviation i.e. anomaly = (value- ref_mean)/ ref_stdev). Red hues indicate below average snow cover; blue hues indicate above-average snow cover. The maps were derived from the NOAA weekly snow cover analysis product, which is made available in digital format by the NOAA Climate Prediction Center.