These systematic errors have typically involved substitution of dew point depression for dew point, station for sea-level pressure, or column shifts. In temporal extent they range from one day or less to twelve months or longer. This temporal scale falls between the single or few observations sought by traditional, outlier-focused analysis, and the multi-year sequences identified by what is usually called inhomogeneity analysis. Application of a variation on what is known in statistical quality control literature as attributes control methodology is described. Flags generated from record-by-record processing are counted by station-month, which counts are then analyzed for patterns of clustering and runs in high counts. The process is semiautomated and guides a technician in identifying precise start and end times of systematic errors, as well as an appropriate correction instruction for each pattern so identified.