A break in a rain shower in southwest Eugene. A view of Eugene from atop Skinner Butte.
| PRECIPITATION | Lane County, Oregon |
| A break in a rain shower in southwest Eugene. A view of Eugene from atop Skinner Butte. |
| Lane County is located in the wet climate
zone of Oregon as opposed to the much drier portion of the state east of the Cascade
Mountains. The distribution of precipitation is uneven throughout Lane County due to
drastic changes in physical geography, mainly concerning changes in elevation. Likewise,
the distribution of precipitation is largely dependent on seasonal changes in the weather. Elevation varies greatly throughout the various regions of Lane County. Coastal areas begin at sea level and rise quickly as one travels east into the Coastal Range. The Valley floors average 400 feet above sea level, and the Cascade Mountains farther to the east tower above at elevations exceeding 10,000 feet above sea level. The differences in levels of precipitation mirror these changes in elevation. The western slopes of the Coastal and Cascade ranges receive far more precipitation than the valley floors due to the condensation of moisture associated with the marine environment of the Pacific Ocean. Air containing moisture must rise to pass over mountain ranges and the vast majority of the precipitation falls on the western side of the mountains, leaving the eastern side much drier. The Coastal and Cascade Ranges receive more than 100 inches of precipitation annually, much of which is in the form of snow during the winter months. The interior of the Willamette Valley typically receives between 40 and 50 inches of precipitation a year. Lane County receives most of its precipitation between the winter months of December and February. Averages for the Eugene area vary between 7 and 9 inches in these months. Rainfall averages for the driest time of the year fluctuate between 0.5 and 2 inches. The data on the map was compiled and analyzed by the Oregon Climate Service, (OCS) using theParameter Regressions on Independent Slopes Model. (PRISM) PRISM is an analytical model that uses weather station data and digital elevation models to generate estimates of monthly and event-based climatic parameters. (OCS 1997) PRISM was designed by a meteorologist to model climatic data and has been used widely to model precipitation in the U.S. and Canada. The following graph illustrates the difference in annual precipitation of two Lane County cities, Florence and Eugene. Florence lies on the coast of the Pacific Ocean while Eugene is located in the central region the Willamette Valley. The mean annual rainfall was calculated using data from the Oregon Climate Service for a twenty-year period. (1977-1997) Precipitation data was collected at Honeyman State Park by Florence and at the Eugene Airport. |
Lane County Precipitation Graph Current Weather Information Sources: Oregon State Service for GIS www.sscgis.state.or.us Oregon Climate Service www.ocs.orst.edu The Weather Channel http://www.weather.com Sources: Meacham, James E. et. al., Atlas of Lane County, Oregon, Eugene: Lane County, 1990 Loy, William G. et. al., Atlas of Oregon, Eugene: University of Oregon Books, 1976.Oregon State Oregon Service Center for GIS (SSCGIS), Salem, OR 97310 www.sscgis.state.or.us Lane Council of Governments, 125 E. 8th Ave., Eugene, OR 97401 (541) 682-4283 All photos taken by Kelly Stats |
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Copyright © Department of Geography, University of Oregon 1999 |
