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during the maximum 6-hr leriod of the maximum 24 hr of the storm. After determination of the lO-mi 24-hr PMP, 6-/24- and 72-/24-hr ratio maps were used to develop PMP values for the 10-mi2 area for these other two key durations. A l-hr 10-mi2 general-storm PMP map was developed using a 1-/6-hr ratio map. The resulting 1-, 6-, 24-, and 72-hr lO-mi2 PMP maps provide the key estimates of PMP for the region. Depth-area relations were developed to enable the user to provide estimates for other area sizes. The depth-area relations are based upon the depth-area characteristics of major storms in and near the region. Local-storm criteria were developed from moisture maximization and transposition of major local-storm amounts throughout the study region. All observed major local storms were transposed to a common 5,000-ft elevation. Procedures are provided to adjust the PMP index values to other elevations. Depth-area and depth-duration relations keyed to the l-mi2 l-hr PMP map at 5,000 ft are provided. 1.5 Definitions All Season. The largest or smallest value of a meteorological variable without regard to the time of the year it occurred. In this report, the largest PMP estimate determined without regard to the time of the year it may occur. Among Storm. A storm characteristic determined when values of various parameters may be determined from different storms. For example, a 6-/24-hr ratio, where the 6-hr value is taken from a different storm than the 24-hr value. AtIIOspheric Forces. The forces that result only from the pressure, temperature and moisture gradients and their relative changes with time over a particular location. Basin Shape. The physical outline of the basin as determined from topographic charts or field survey. Dew Point. The temperature to which a given parcel of air must be cooled at constant pressure and constant water-vapor content in order for saturation to occur. Effective Elevation. The elevation at a point determined from a chart where topographic contours have been smoothed to reflect the effect of terrain on the precipitation process for a particular magnitude of storm. The actual elevation at the point may be either higher or lower than the effective elevation. Effective Storm Duration. The time period within which 90 percent of the total storm precipitation occurs. Generalized. When used as an adjective to modify names such as PMP or estimates or charts, is to be taken in the sense of "comprehensive," i.e., pertaining to all things belonging to a group or category. Thus, a generalized PMP map for a specific area and duration defines PMP for all points in the region; no location is excluded. General Storm. A storm event which usually produces precipitation over areas in excess of 500 mi 2 and durations longer than 6 hr and is associated wi th a maj or synoptic weather feature. 5