The Bonneville Power Administration (BPA) is a federal agency, under the U.S. Department of Energy, that markets wholesale electrical power and operates and markets transmission services in the Pacific Northwest. The power comes from 31 federal hydro projects, one nonfederal nuclear plant and several other nonfederal power plants. The hydro projects and the electrical system are known as the Federal Columbia River Power System. About 45 percent of the electric power used in the Northwest comes from BPA. BPA’s transmission system accounts for about three-quarters of the region’s high-voltage grid, and includes major transmission links with other regions. BPA is a self-funding agency, which pays for its costs through power and transmission sales. Both power and transmission are sold at cost, and BPA repays any borrowing from the U.S. Treasury with interest. The revenues BPA earns help fulfill its public responsibilities, which include low-cost and reliable power and investments in energy conservation and renewable resources. BPA also funds the region’s efforts to protect and rebuild fish and wildlife populations in the Columbia River Basin. Although about 60 percent of the region’s electricity comes from hydroelectric sources, BPA’s generation is about 80% hydroelectric. The heavy dependency of the region on hydro generation as well as the increasing demand on the rivers for non-power uses and other obligations has created an ever-increasing need for accurate weather and streamflow forecasts. While accuracy once only pertained to the short range (1-7 days), the reduced flexibility of the hydro system, market competition, and reliability issues have also created a need for accurate long-range forecasts. For a drainage area of roughly 250,000 square miles, with diverse terrain ranging from the Rocky Mountains to high desert plateaus, this provides a challenge to any forecaster. In addition, the majority of BPA’s load resides west of the Cascade Range, in a climate regime much different than the source region of its hydro generation. Skill and forecast products must be developed to support both load and streamflow demands. The subject of this presentation will be the issues and challenges surrounding forecasting for a large river system and service area in the Pacific Northwest.