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The climate of Moffat County is classified as semiarid and is characterized by low precipitation, large daily temperature range, low humidity, frequent wind, and abundant sunshine. The prevailing direction of air movement to the region is from the west. On arrival, airmasses from the west are comparatively dry due to long travel over land and loss of moisture Over mountain ranges. However, the primary sources of moisture are the Pacific Ocean and the Gulf of Mexico. Generally, airmasses from the Pacific Ocean dominate from October through April, while airmasses from the Gulf of Mexico dominate during late spring and summer. Temperatures in the summer are very mild; the record high is lOQoF. Temperature maximums above 950F occur infrequently. The lowest observed temperature in the Craig area of Moffat County was -450F in January 1963. The mean temperatures range from approximately 170F in January to approximately 670F in July. Cooler temperatures prevail in higher mountain areas. The growing Season usually extends for 60 to 120 days. Normal annual precipitation varies with elevation and ranges from approximately 14 inches at Craig to 80 inches (estimated) at high elevations in the Park Range. Most of the annual precipitation in high elevation areas occurs as snow from December to April and, beginning in October, a deep snowpack accumulates. Snowmelt begins in late April and continues well into June or early July. Snowfall in Moffat County is not extremely heavy, with annual totals ranging from 33 to 77 inches. Rainfall may occur over the Yampa River basin and convective type cloudburst storms fre- quently occur in summer. The flood plains of all the streams studied are primarily undevel- oped, with the following exceptions: the lower portion of Fortifi- cation Creek has light-industrial development, Cedar Mountain Gulch has a mobile home trailer park north of U.S. Highway 40 and commercial development south of U.S. Highway 40, the Pine Ridge Gulch flood plain is occupied by light-industrial development downstream of State Highway 13 and by commercial and residential development upstream of State Highway 13. 2.3 Principal Flood Problems Major flooding in the Moffat County area has been the result of rapidly melting snow, sometimes augmented by rainfall, during the period from March through June, or precipitated by ice jams in late winter or early spring. Snowmelt flooding is characterized by moderate peak flows. large volume of runoff, long duration, and marked diurnal fluctuation of flow. Major flooding from rainfall alone is not known to have occurred in the Craig area, but there is no reason to conclude that very large floods resulting from 7