Forest Trail Explorer

US Forest Service and Southern Research Station

Precipitation Variability

Precipitation is essential to both ecosystem processes and to water supplies for municipalities. Precipitation is any form of water – drizzle, rain, sleet, snow, graupel (soft hail or snow pellets), or hail – that falls from the atmosphere and reaches the ground.

Western North Carolina has some of the most variable average precipitation in the southeastern United States. In fact, the wettest and driest points in Western North Carolina are separated by only 50 miles. Elevation gradients of the mountains contribute to the differences in precipitation, which can range from 100 inches to 36 inches per year.

As an example, consider average rainfall in two towns – Lake Toxaway and Asheville – that according to the State Climate Office of North Carolina are the wettest and driest official weather recording stations in the region, respectively. Lake Toxaway, located in Transylvania County, has average annual precipitation of around 92 inches, and sits at the southern edge of the Blue Ridge Escarpment. Moist air lifted over the mountains drops heavy amounts of rain on this high-elevation town; nearby areas are wet enough to be considered rain forests, and waterfalls abound. In contrast, the city of Asheville, in Buncombe County, has average annual precipitation of around 37 inches, and sits in the French Broad River basin. Shielded from the prevailing moist winds from the south and west by the Balsam and Smoky Mountains (where most of the rainfall is squeezed out), this area is the driest in the entire state of North Carolina.

Elevation gradients also contribute to the various forms of precipitation the region receives. For example, lower elevations receive most precipitation as rainfall, whereas the tallest mountain peaks receive up to 50 inches of snowfall each year.

The above content is a part of the Western North Carolina Vitality Index. To view the full report, visit www.wncvitalityindex.org.

Forest Inventory and Analysis Resources

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References

Oregon State University, PRISM Group. Accessed from: http://www.prism.oregonstate.edu/.

Moore Myers, J. June 2007. Average derived from yearly average observations in Avery, Henderson, Macon, Madison, and Haywood counties (1893 to 2006). Raleigh, NC: USDA Forest Service, Southern Research Station.